Optical module for spectral analysis

ABSTRACT

An optical module includes: a mirror unit having a movable mirror and a fixed mirror; a beam splitter unit; a light incident unit that causes measurement light to be incident to the beam splitter unit; a first light detector that detects interference light of the measurement light; a second light source that emits laser light; a second light detector that detects interference light of the laser light; a first mirror that allows the measurement light to be transmitted therethrough and reflects the laser light; a second mirror that reflects a part of the laser light and allows the remainder of the laser light to be transmitted therethrough; a third mirror that reflects the laser light; and a return light suppressing unit that suppresses the laser light from becoming return light, and is disposed on a side opposite to the second optical device with respect to the second mirror.

TECHNICAL FIELD

The present disclosure relates to an optical module.

BACKGROUND

As a micro electro mechanical system (MEMS) device constituted by a silicon on insulator (SOI) substrate, an optical module in which respective units which constitute an interference optical system are formed in the SOI substrate is known (for example, refer to Japanese Translation of PCT International Application Publication No. 2012-524295).

SUMMARY

The above-described optical module can provide high-accuracy fourier transformation type infrared spectral analyzer (FTIR), and thus the optical module has attracted attention.

An object of the present disclosure is to provide an optical module capable of realizing high-accuracy spectral analysis with a simple configuration.

According to an aspect of the present disclosure, there is provided an optical module including: a mirror unit that includes a base that has a first surface, a movable mirror that is supported in the base to be movable along a first direction intersecting the first surface, and a fixed mirror of which a position with respect to the base is fixed; a beam splitter unit that is disposed on one side of the mirror unit in the first direction, and constitutes an interference optical system in combination with the movable mirror and the fixed mirror; a light incident unit that causes measurement light that is incident from a first light source through a measurement target, or measurement light that occurs from a measurement target to be incident to the beam splitter unit; a first optical device that is a first light detector that detects interference light of the measurement light which is emitted from the beam splitter unit; a second optical device that is one of a second light source that emits laser light to be incident to the beam splitter unit and a second light detector that detects interference light of the laser light which is emitted from the beam splitter unit, and is disposed on one side of the first optical device in a direction intersecting an optical axis of the first optical device to face the same side as in the first optical device; a third optical device that is the other of the second light source and the second light detector, and is disposed on the one side of the second optical device in the direction intersecting the optical axis of the first optical device to face the same side as in the first optical device; a first mirror that is disposed to face the beam splitter unit and the first optical device as a dichroic mirror that has a function of allowing the measurement light to be transmitted therethrough and reflecting the laser light or a function of reflecting the measurement light and allowing the laser light to be transmitted therethrough, and is inclined with respect to the optical axis of the first optical device; a second mirror that is disposed to face the first mirror and the second optical device as a mirror that has a function of reflecting a part of the laser light and allowing the remainder of the laser light to be transmitted therethrough, and is parallel to the first mirror, a third mirror that is disposed to face the second mirror and the third optical device as a mirror that has a function of reflecting the laser light, and is parallel to the second mirror; and a return light suppressing unit that has a function of suppressing the incident laser light from becoming return light, and is disposed on a side opposite to the second optical device with respect to the second mirror.

In the optical module, the first optical device that is the first light detector, the second optical device that is one of the second light source and the second light detector, and the third optical device that is the other of the second light source and the second light detector are disposed to face the same side. Accordingly, it is possible to constitute the interference optical system relating to the measurement light and the interference optical system relating to the laser light with a simple layout, and it is possible to carry out spectral analysis on the basis of a detection result of the interference light of the measurement light while acquiring a position of the movable mirror in the first direction on the basis of a detection result of the interference light of the laser light. In addition, the return light suppressing unit having a function of suppressing incident laser light from becoming return light is disposed on a side opposite to the second optical device with respect to the second mirror. Accordingly, it is possible to prevent a component other than a component reflected by each of the movable mirror and the fixed mirror from being superimposed on the interference light of the laser light, and thus it is possible to acquire a position of the movable mirror in the first direction with accuracy. In addition, the first optical device that is the first light detector, the second optical device that is one of the second light source and the second light detector, and the third optical device that is the other of the second light source and the second light detector are disposed to be aligned in this order. Accordingly, it is possible to shorten a length of an optical path between the beam splitter unit and the first light detector, and thus it is possible to detect the interference light of the measurement light with a sufficient light amount. As described above, according to the optical module, it is possible to realize high-accuracy spectral analysis with a simple configuration.

In the optical module of the present disclosure, the return light suppressing unit may be a part of a support that supports the second mirror. Accordingly, it is possible to suppress an increase in the number of parts.

In the optical module of the present disclosure, the return light suppressing unit may be a member different from a support that supports the second mirror. Accordingly, it is possible to improve the degree of freedom of design of the support and the return light suppressing unit.

The optical module of the present disclosure may further include a filter that has a function of allowing the measurement light to be transmitted therethrough and cutting off the laser light, and is disposed on the light incident unit side with respect to the beam splitter unit. Accordingly, it is possible to prevent light of sensitivity wavelength component of the second light detector from being incident to the beam splitter unit from the light incident unit, and thus it is possible to acquire a position of the movable mirror in the first direction with accuracy on the basis of a detection result of the interference light of the laser light.

In the optical module of the present disclosure, the second optical device may be the second light detector, and the third optical device may be the second light source. Accordingly, it is possible to realize simplification of a configuration of a circuit substrate for signal input/output with respect to the first optical device, the second optical device, and the third optical device.

According to another aspect of the present disclosure, there is provided an optical module including: a mirror unit that includes a base that has a first surface, a movable mirror that is supported in the base to be movable along a first direction intersecting the first surface, and a fixed mirror of which a position with respect to the base is fixed; a beam splitter unit that is disposed on one side of the mirror unit in the first direction, and constitutes an interference optical system in combination with the movable mirror and the fixed mirror, a first optical device that is a first light source that emits measurement light to be incident to the beam splitter unit; a first light detector that detects interference light of the measurement light which is emitted from the beam splitter unit and is incident through a measurement target; a second optical device that is one of a second light source that emits laser light to be incident to the beam splitter unit and a second light detector that detects interference light of the laser light which is emitted from the beam splitter unit, and is disposed on one side of the first optical device in a direction intersecting an optical axis of the first optical device to face the same side as in the first optical device; a third optical device that is the other of the second light source and the second light detector, and is disposed on the one side of the second optical device in the direction intersecting the optical axis of the first optical device to face the same side as in the first optical device; a first mirror that is disposed to face the beam splitter unit and the first optical device as a dichroic mirror that has a function of allowing the measurement light to be transmitted therethrough and reflecting the laser light or a function of reflecting the measurement light and allowing the laser light to be transmitted therethrough, and is inclined with respect to the optical axis of the first optical device; a second mirror that is disposed to face the first mirror and the second optical device as a mirror that has a function of reflecting a part of the laser light and allowing the remainder of the laser light to be transmitted therethrough, and is parallel to the first mirror; a third mirror that is disposed to face the second mirror and the third optical device as a mirror that has a function of reflecting the laser light, and is parallel to the second mirror; and a return light suppressing unit that has a function of suppressing the incident laser light from becoming return light, and is disposed on a side opposite to the second optical device with respect to the second mirror.

In the optical module, the first optical device that is the first light source, the second optical device that is one of the second light source and the second light detector, and the third optical device that is the other of the second light source and the second light detector are disposed to face the same side. Accordingly, it is possible to constitute the interference optical system relating to the measurement light and the interference optical system relating to the laser light with a simple layout, and it is possible to carry out spectral analysis on the basis of a detection result of the interference light of the measurement light while acquiring a position of the movable mirror in the first direction on the basis of a detection result of the interference light of the laser light. In addition, the return light suppressing unit having a function of suppressing incident laser light from becoming return light is disposed on a side opposite to the second optical device with respect to the second mirror. Accordingly, it is possible to prevent a component other than a component reflected by each of the movable mirror and the fixed mirror from being superimposed on the interference light of the laser light, and thus it is possible to acquire a position of the movable mirror in the first direction with accuracy. In addition, the first optical device that is the first light source, the second optical device that is one of the second light source and the second light detector, and the third optical device that is the other of the second light source and the second light detector are disposed to be aligned in this order. Accordingly, it is possible to shorten a length of an optical path between the first light source and the beam splitter unit, and it is possible to detect the interference light of the measurement light with a sufficient light amount. As described above, according to the optical module, it is possible to realize high-accuracy spectral analysis with a simple configuration.

In the optical module of the present disclosure, the second optical device may the second light source, and the third optical device may be the second light detector. Accordingly, it is possible to realize simplification of a configuration of a circuit substrate for signal input/output with respect to the first optical device, the second optical device, and the third optical device.

In the optical module of the present disclosure, on the one side of the beam splitter unit in the first direction, the first optical device, the second optical device, and the third optical device may be disposed to face the other side in the first direction. Accordingly, it is possible to realize a reduction in size of the optical module in a direction intersecting the first direction.

In the optical module of the present disclosure, on one side of the mirror unit in a second direction intersecting the first direction, the first optical device, the second optical device, and the third optical, device may be disposed to face the one side in the first direction. Accordingly, it is possible to realize a reduction in size of the optical module in the first direction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an optical module of an embodiment.

FIG. 2 is a plan view of a mirror unit illustrated in FIG. 1.

FIG. 3 is a cross-sectional view of the mirror unit which is taken along line III-III illustrated in FIG. 2.

FIG. 4 is a cross-sectional view of the mirror unit which is taken along line IV-IV illustrated in FIG. 2.

FIG. 5 is a schematic cross-sectional view of a mirror device which is taken along line V-V illustrated in FIG. 2.

FIG. 6 is a partially enlarged view of the mirror device illustrated in FIG. 2.

FIG. 7 is a plan view of an optical function member illustrated in FIG. 2.

FIG. 8 is a cross-sectional view of the optical module which is taken along line VIII-VIII illustrated in FIG. 1.

FIG. 9 is a cross-sectional view of the optical module which is taken along line IX-IX illustrated in FIG. 1.

FIG. 10 is a schematic cross-sectional view of the mirror unit and a beam splitter unit which are illustrated in FIG. 1.

FIG. 11 is a graph illustrating a spectrum for describing a leakage error.

FIG. 12 is a cross-sectional view of an optical module according to a second embodiment.

FIG. 13 is a schematic cross-sectional view of an optical module according to a third embodiment.

FIG. 14 is a schematic cross-sectional view of an optical module according to a fourth embodiment.

DETAILED DESCRIPTION

Hereinafter, an embodiment of the invention will be described in detail with reference to the accompanying drawings. The same reference numeral will be given to the same or equivalent parts in the respective drawings, and redundant description thereof will be omitted.

First Embodiment

[Configuration of Optical Module]

As illustrated in FIG. 1, an optical module 1A includes a mirror unit 2, a beam splitter unit 3, a light incident unit 4, a first light detector 6, a second light source 7, a second light detector 8, a support 9, a first support structure 11, and a second support structure 12. The mirror unit 2 is disposed on one side of the support 9 in a Z-axis direction (first direction), and is attached to the support 9, for example, by an adhesive. For example, the support 9 is formed of copper tungsten, and has a rectangular plate shape. The mirror unit 2 includes a movable mirror 22 that moves in the Z-axis direction, and a fixed mirror 16 of which a position is fixed (details thereof will be described later). For example, the Z-axis direction is a vertical direction, and the one side in the Z-axis direction is an upper side.

The beam splitter unit 3 is disposed on one side of the mirror unit 2 in the Z-axis direction, and is supported by the first support structure 11. The first support structure 11 is attached to the support 9, for example, by an adhesive. The light incident unit 4 is disposed on one side of the beam splitter unit 3 in an X-axis direction (a third direction perpendicular to the first direction), and is supported by the second support structure 12. The first light detector 6, the second light source 7, and the second light detector 8 are disposed on the one side of the beam splitter unit 3 in the Z-axis direction, and are supported by the second support structure 12. The second support structure 12 is attached to the support 9, for example, by a bolt.

In the optical module 1A, an interference optical system is constituted by the beam splitter unit 3, the movable mirror 22, and the fixed mirror 16 with respect to each of measurement light L0 and laser light L10. The interference optical system which is constituted with respect to each of the measurement light L0 and the laser light L10 is, for example, a Michelson interference optical system.

With regard to the measurement light L0, interference light L1 of measurement light is detected as follows. That is, when the measurement light L0 that is incident from a first light source (not illustrated) through a measurement target (not illustrated) or the measurement light L0 that is generated from the measurement target (for example, light emitted from the measurement target itself) is incident to the beam splitter unit 3 from the light incident unit 4, the measurement light L0 is divided into a part and the remainder in the beam splitter unit 3. The part of the measurement light L0 is reflected by the movable mirror 22 that reciprocates in the Z-axis direction, and returns to the beam splitter unit 3. On the other hand, the remainder of the measurement light L0 is reflected by the fixed mirror 16 and returns to the beam splitter unit 3. The part and the remainder of the measurement light L0, which returns to the beam splitter unit 3, are emitted from the beam splitter unit 3 as the interference light L1, and the interference light L1 of the measurement light is detected by the first light detector 6.

With regard to the laser light L10, interference light L11 of laser light is detected as follows. That is, when the laser light L10 emitted from the second light source 7 is incident to the beam splitter unit 3, the laser light L10 is divided into a part and the remainder in the beam splitter unit 3. The part of the laser light L10 is reflected by the movable mirror 22 that reciprocates in the Z-axis direction, and returns to the beam splitter unit 3. On the other hand, the remainder of the laser light L10 is reflected by the fixed mirror 16 and returns to the beam splitter unit 3. The part and the remainder of the laser light L10, which return to the beam splitter unit 3, are emitted from the beam splitter unit 3 as the interference light L11, and the interference light L11 of the laser light is detected by the second light detector 8.

According to the optical module 1A, measurement of a position of the movable mirror 22 in the Z-axis direction can be measured based on a detection result of the interference light L11 of the laser light, and spectral analysis with respect to the measurement target can be performed based on a measurement result of the position, and a detection result of the interference light L1 of the measurement light.

[Configuration of Mirror Unit]

As illustrated in FIG. 2, FIG. 3, and FIG. 4, the mirror unit 2 includes a mirror device (optical device) 20, an optical function member 13, the fixed mirror 16, and a stress mitigation substrate 17. The mirror device 20 includes a base 21, the movable mirror 22, and a drive unit 23.

The base 21 includes a first surface 21 a (surface on the one side in the Z-axis direction) and a second surface 21 b opposite to the first surface 21 a. Each of the first surface 21 a and the second surface 21 b is a main surface of the base 21. For example, the base 21 has a rectangular plate shape, and a size of approximately 10 mm×15 mm×0.35 mm (thickness). The movable mirror 22 includes a mirror surface (optical function unit) 22 a, and a movable unit 22 b in which the mirror surface 22 a is disposed. The movable mirror 22 (movable unit 22 b) is supported in the base 21 so that the movable mirror 22 can move in the Z-axis direction perpendicular to the first surface 21 a (a first direction perpendicular to a first surface). The drive unit 23 moves the movable mirror 22 in the Z-axis direction.

A pair of light passage openings 24 and 25 are provided in the mirror device 20. The pair of light passage openings 24 and 25 are respectively disposed on both sides of the movable mirror 22 in the X-axis direction. The light passage opening (first light passage portion) 24 constitutes a first portion of an optical path between the beam splitter unit 3 and the fixed mirror 16. In this embodiment, the light passage opening 25 does not function as a light passage opening.

Here, a configuration of the mirror device 20 will be described in detail with reference to FIG. 2, FIG. 5, and FIG. 6. FIG. 5 is a schematic cross-sectional view of the mirror device 20 illustrated in FIG. 3, and FIG. 5 schematically illustrates the mirror device 20, for example, in a state in which dimensions in the Z-axis direction are enlarged in comparison to actual dimensions.

The base 21, the movable unit 22 b of the movable mirror 22, and the drive unit 23 are constituted by a silicon on insulator (SOI) substrate (semiconductor substrate) 100. That is, the mirror device 20 is constituted by the SOI substrate 100. For example, the mirror device 20 is formed in a rectangular plate shape. The SOI substrate 100 includes a support layer 101, a device layer 102, and an intermediate layer 103. The support layer 101 is a first silicon layer (a first semiconductor layer). The device layer 102 is a second silicon layer (a second semiconductor layer). The intermediate layer 103 is an insulating layer that is disposed between the support layer 101 and the device layer 102. The SOT substrate 100 includes the support layer 101, the intermediate layer 103, and the device layer 102 in this order from the one side in the Z-axis direction.

The base 21 is constituted by a part of the support layer 101, the device layer 102, and the intermediate layer 103. The first surface 21 a of the base 21 is a surface of the support layer 101 which is opposite to the intermediate layer 103. The second surface 21 b of the base 21 is a surface of the device layer 102 which is opposite to the intermediate layer 103. The support layer 101 that constitutes the base 21 is thicker than the device layer 102 that constitutes the base 21. For example, the thickness of the support layer 101 that constitutes the base 21 is approximately four times the thickness of the device layer 102 that constitutes the base 21. As will be described later, in the mirror unit 2, the second surface 21 b of the base 21 and a third surface 13 a of the optical function member 13 are jointed to each other (refer to FIG. 3 and FIG. 4).

The movable mirror 22 is disposed in a state in which an intersection between an axial line R1 and an axial line R2 is set as the central position (gravity center position). The axial line R1 is a straight line that extends in the X-axis direction. The axial line R2 is a straight line that extends in a Y-axis direction (a second direction that is perpendicular to the first direction and the third direction). When viewed from the Z-axis direction, in the mirror device 20, a portion other than a portion that overlaps a sixth surface 21 d of the base 21 to be described later has a shape that is linearly symmetric to each of the axial line R1 and the axial line R2.

The movable mirror 22 (movable unit 22 b) includes an arrangement portion 221, a frame portion 222, a pair of connection portions 223, and a beam portion 224. The arrangement portion 221, the frame portion 222, and the pair of connection portions 223 are constituted by a part of the device layer 102. The arrangement portion 221 has a circular shape when viewed from the Z-axis direction. The arrangement portion 221 includes a central portion 221 a and an edge portion 221 b. For example, the mirror surface 22 a is provided on a surface 221 as of the central portion 221 a on the one side in the Z-axis direction by forming a metal film (metal layer) thereon. The mirror surface 22 a extends perpendicular to the Z-axis direction, and has a circular shape. The surface 221 as of the central portion 221 a is a surface on the intermediate layer 103 side in the device layer 102. The mirror surface 22 a is located on the other side in the Z-axis direction in comparison to the first surface 21 a of the base 21. In other words, the first surface 21 a is located on the one side in the Z-axis direction in comparison to the mirror surface 22 a. The edge portion 221 b surrounds the central portion 221 a when viewed from the Z-axis direction.

The frame portion 222 extends in an annular shape to surround the arrangement portion 221 with a predetermined gap from the arrangement portion 221 when viewed from the Z-axis direction. For example, the frame portion 222 has a circular ring shape when viewed from the Z-axis direction. Each of the pair of connection portions 223 connects the arrangement portion 221 and the frame portion 222 to each other. The pair of connection portions 223 are respectively disposed on both sides of the arrangement portion 221 in the Y-axis direction.

The beam portion 224 is constituted by the support layer 101 and the intermediate layer 103 which are disposed on the device layer 102. The beam portion 224 includes an inner beam portion 224 a, an outer beam portion 224 b, and a pair of connection beam portions 224 c. The inner beam portion 224 a is disposed on a surface of the edge portion 221 b on the one side in the Z-axis direction. The inner beam portion 224 a surrounds the mirror surface 22 a when viewed from the Z-axis direction. For example, an outer edge of the inner beam portion 224 a extends along an outer edge of the arrangement portion 221 with a predetermined gap from the outer edge of the arrangement portion 221 when viewed from the Z-axis direction. An inner edge of the inner beam portion 224 a extends along an outer edge of the mirror surface 22 a with a predetermined gap from the outer edge of the mirror surface 22 a when viewed from the Z-axis direction. An end surface 224 as of the inner beam portion 224 a on the one side in the Z-axis direction is located on the one side in the Z-axis direction in comparison to the mirror surface 22 a.

The outer beam portion 224 b is disposed on a surface of the frame portion 222 on the one side in the Z-axis direction. The outer beam portion 224 b surrounds the inner beam portion 224 a and the mirror surface 22 a when viewed from the Z-axis direction. For example, an outer edge of the outer beam portion 224 b extends along an outer edge of the frame portion 222 with a predetermined gap from the outer edge of the frame portion 222 when viewed from the Z-axis direction. An inner edge of the outer beam portion 224 b extends along an inner edge of the frame portion 222 with a predetermined gap from the inner edge of the frame portion 222 when viewed from the Z-axis direction. An end surface 224 bs of the outer beam portion 224 b on the one side in the Z-axis direction is located on the one side in the Z-axis direction in comparison to the mirror surface 22 a.

The pair of connection beam portions 224 c are respectively disposed on surfaces of the pair of connection portions 223 on the one side in the Z-axis direction. The connection beam portions 224 c connect the inner beam portion 224 a and the outer beam portion 224 b to each other. End surfaces 224 cs of the connection beam portions 224 c on the one side in the Z-axis direction are located on the one side in the Z-axis direction in comparison to the mirror surface 22 a.

The thickness of the inner beam portion 224 a, the thickness of the outer beam portion 224 b, and the thickness of the respective connection beam portions 224 c in the Z-axis direction are the same as each other. That is, the thickness of the support layer 101 that constitutes the inner beam portion 224 a, the outer beam portion 224 b, and the respective connection beam portions 224 c is the same in each case. The end surface 224 as of the inner beam portion 224 a, the end surface 224 bs of the outer beam portion 224 b, and the end surfaces 224 cs of the respective connection beam portions 224 c are located on the same plane perpendicular to the Z-axis direction. The support layer 101 that constitutes the inner beam portion 224 a, the outer beam portion 224 b, and the respective connection beam portions 224 c is thinner than the support layer 101 that constitutes the base 21. Accordingly, the end surfaces 224 as, 224 bs, and 224 cs are located on the one side in the Z-axis direction in comparison to the first surface 21 a of the base 21. In other words, the first surface 21 a is located on the other side in the Z-axis direction in comparison to the end surfaces 224 as, 224 bs, and 224 cs.

When viewed from the Z-axis direction, a width of the outer beam portion 224 b is wider than a width of the inner beam portion 224 a. The width of the inner beam portion 224 a when viewed from the Z-axis direction is a length of the inner beam portion 224 a in a direction perpendicular to the extending direction of the inner beam portion 224 a, and is a length of the inner beam portion 224 a in a radial direction of the inner beam portion 224 a in this embodiment. This is also true of a width of the outer beam portion 224 b when viewed from the Z-axis direction. A width of each of the connection beam portions 224 c is wider than the width of each of the inner beam portion 224 a and the outer beam portion 224 b. The width of each of the connection beam portion 224 c is a length of each of the connection beam portion 224 c along the extending direction of the inner beam portion 224 a.

The drive unit 23 includes a first elastic support unit 26, a second elastic support unit 27, and an actuator unit 28. The first elastic support unit 26, the second elastic support unit 27, and the actuator unit 28 are constituted by a part of the device layer 102.

Each of the first elastic support unit 26 and the second elastic support unit 27 is connected between the base 21 and the movable mirror 22. The first elastic support unit 26 and the second elastic support unit 27 support the movable mirror 22 so that the movable mirror 22 (movable unit 22 b) can move in the Z-axis direction.

The first elastic support unit 26 includes a pair of levers 261, a first link member 262, a second link member 263, a pair of beam members 264, an intermediate member 265, a pair of first torsion bars (first torsion support portions) 266, a pair of second torsion bars (second torsion support portions) 267, a pair of non-linearity mitigation springs 268, and a plurality of electrode support portions 269.

The pair of levers 261 are respectively disposed on both sides of the light passage opening 24 in the Y-axis direction, and face each other in the Y-axis direction. Each of the levers 261 has a plate shape that extends along a plane perpendicular to the Z-axis direction. The lever 261 includes a first portion 261 a, a second portion 261 b that is disposed on a side opposite to the movable mirror 22 with respect to the first portion 261 a, and a third portion 261 c that is connected to the first portion 261 a and the second portion 261 b. The first portion 261 a and the second portion 261 b extend in the X-axis direction. A length of the first portion 261 a in the X-axis direction is shorter than a length of the second portion 261 b in the X-axis direction. The third portions 261 c of the pair of levers 261 obliquely extend to be spaced away from each other as going away from the movable mirror 22.

The first link member 262 bridges first ends 261 d of the pair of levers 261 on a side opposite to the movable mirror 22. The first link member 262 has a plate shape that extends along a plane perpendicular to the Z-axis direction, and extends in the Y-axis direction. The second link member 263 bridges second ends 261 e of the pair of levers 261 on the movable mirror 22 side. The second link member 263 has a plate shape that extends along a plane perpendicular to the Z-axis direction, and extends in the Y-axis direction. A width of the second link member 263 in the X-axis direction is narrower than a width of the first link member 262 in the X-axis direction. A length of the second link member 263 in the Y-axis direction is shorter than a length of the first link member 262 in the Y-axis direction.

The pair of beam members 264 respectively bridge the second portions 261 b of the pair of levers 261 and the first link member 262. The respective beam members 264 have a plate shape that extends along a plane perpendicular to the Z-axis direction. The pair of beam members 264 obliquely extend to approach each other as going away from the movable mirror 22. The pair of levers 261, the first link member 262, the second link member 263, and the pair of beam members 264 define the light passage opening 24. The light passage opening 24 has a polygonal shape when viewed from the Z-axis direction. For example, the light passage opening 24 is a cavity (hole). Alternatively, a material having optical transparency with respect to the measurement light L0 and the laser light L10 may be disposed in the light passage opening 24.

The intermediate member 265 has a plate shape that extends along a plane perpendicular to the Z-axis direction, and extends in the Y-axis direction. The intermediate member 265 is disposed between the movable mirror 22 and the second link member 263 (in other words, between the movable mirror 22 and the light passage opening 24). The intermediate member 265 is connected to the movable mirror 22 through the non-linearity mitigation springs 268 as to be described later.

The pair of first torsion bars 266 respectively bridge the first end 261 d of one lever 261 and the base 21, and the first end 261 d of the other lever 261 and the base 21. That is, the pair of first torsion bars 266 are respectively connected between the pair of levers 261 and the base 21. The first torsion bars 266 extend in the Y-axis direction. The pair of first torsion bars 266 are disposed on the same central line parallel to the Y-axis direction. In this embodiment, the central line of the first torsion bars 266 and the central line of the first link member 262 are located on the same straight line. A protrusion 261 f that protrudes outward in the Y-axis direction is provided in each of the first ends 261 d of the levers 261, and each of the first torsion bars 266 is connected to the protrusion 261 f.

The pair of second torsion bars 267 respectively bridge the second end 261 e of one lever 261 and one end of the intermediate member 265, and the second end 261 e of the other lever 261 and the other end of the intermediate member 265. That is, the pair of second torsion bars 267 are respectively connected between the pair of levers 261 and the movable mirror 22. The respective second torsion bars 267 extend in the Y-axis direction. The pair of second torsion bars 267 are disposed on the same central line parallel to the Y-axis direction.

The pair of non-linearity mitigation springs 268 are connected between the movable mirror 22 and the intermediate member 265. That is, the pair of non-linearity mitigation springs 268 are connected between the movable mirror 22 and the second torsion bar 267. Each of the non-linearity mitigation springs 268 includes a meandering portion 268 a that extends in a meandering manner when viewed from the Z-axis direction. The meandering portion 268 a includes a plurality of straight portions 268 b which extend in the Y-axis direction and are aligned in the X-axis direction, and a plurality of folded portions 268 c which alternately connect both ends of the plurality of straight portions 268 b. One end of the meandering portion 268 a is connected to the intermediate member 265, and the other end of the meandering portion 268 a is connected to the frame portion 222. In the meandering portion 268 a, a portion on the frame portion 222 side has a shape along the outer edge of the frame portion 222.

The non-linearity mitigation spring 268 is constituted as follows. In a state in which the movable mirror 22 has moved in the Z-axis direction, the amount of deformation of the non-linearity mitigation spring 268 around the Y-axis direction becomes smaller than the amount of deformation of each of the first torsion bar 266 and the second torsion bar 267 around the Y-axis direction, and the amount of deformation of the non-linearity mitigation spring 268 in the X-axis direction becomes larger than the amount of deformation of each of the first torsion bar 266 and the second torsion bar 267 in the X-axis direction. Accordingly, it is possible to suppress occurrence of non-linearity in twist deformation of the first torsion bar 266 and the second torsion bar 267, and it is possible to suppress deterioration of control characteristics of the movable mirror 22 due to the non-linearity. The amount of deformation of the first torsion bar 266, the second torsion bar 267, and the non-linearity mitigation spring 268 around the Y-axis direction represents, for example, an absolute value of a twist amount (twist angle). The amount of deformation of the first torsion bar 266, the second torsion bar 267, and the non-linearity mitigation spring 268 in the X-axis direction represents, for example, an absolute value of a deflection amount. The amount of deformation of a member around the Y-axis direction represents the amount of deformation of the member in a peripheral direction of a circle of which the center is set to an axial line that passes through the center of the member and is parallel to the Y-axis. This is also true of first torsion bars 276, second torsion bars 277, and a non-linearity mitigation spring 278 to be described later.

The plurality of electrode support portions 269 include a pair of first electrode support portions 269 a, a pair of second electrode support portions 269 b, and a pair of third electrode support portions 269 c. Each of the electrode support portions 269 a, 269 b, and 269 c has a plate shape that extends along a plane perpendicular to the Z-axis direction, and extends in the Y-axis direction. Each of the electrode support portions 269 a, 269 b, and 269 c extends from the second portion 261 b of the lever 261 toward a side opposite to the light passage opening 24. The pair of first electrode support portions 269 a are disposed on the same central line parallel to the Y-axis direction. The pair of second electrode support portions 269 b are disposed on the same central line parallel to the Y-axis direction. The pair of third electrode support portions 269 c are disposed on the same central line parallel to the Y-axis direction. In the X-axis direction, the first electrode support portions 269 a, the second electrode support portions 269 b, and the third electrode support portions 269 c are aligned in this order from the movable mirror 22 side.

The second elastic support unit 27 includes a pair of levers 271, a first link member 272, a second link member 273, a pair of beam members 274, an intermediate member 275, a pair of first torsion bars (first torsion support portions) 276, a pair of second torsion bars (second torsion support portions) 277, a pair of non-linearity mitigation springs 278, and a plurality of electrode support portions 279.

The pair of levers 271 are respectively disposed on both sides of the light passage opening 25 in the Y-axis direction, and face each other in the Y-axis direction. Each of the levers 271 has a plate shape that extends along a plane perpendicular to the Z-axis direction. The lever 271 includes a first portion 271 a, a second portion 271 b that is disposed on a side opposite to the movable mirror 22 with respect to the first portion 271 a, and a third portion 271 c that is connected to the first portion 271 a and the second portion 271 b. The first portion 271 a and the second portion 271 b extend in the X-axis direction. A length of the first portion 271 a in the X-axis direction is shorter than a length of the second portion 271 b in the X-axis direction. The third portions 271 c of the pair of levers 271 obliquely extend to be spaced away from each other as going away from the movable mirror 22.

The first link member 272 bridges first ends 271 d of the pair of levers 271 on a side opposite to the movable mirror 22. The first link member 272 has a plate shape that extends along a plane perpendicular to the Z-axis direction, and extends in the Y-axis direction. The second link member 273 bridges second ends 271 e of the pair of levers 271 on the movable mirror 22 side. The second link member 273 has a plate shape that extends along a plane perpendicular to the Z-axis direction, and extends in the Y-axis direction. A width of the second link member 273 in the X-axis direction is narrower than a width of the first link member 272 in the X-axis direction. A length of the second link member 273 in the Y-axis direction is shorter than a length of the first link member 272 in the Y-axis direction.

The pair of beam members 274 respectively bridge the second portions 271 b of the pair of levers 271 and the first link member 272. The respective beam members 274 have a plate shape that extends along a plane perpendicular to the Z-axis direction. The pair of beam members 274 obliquely extend to approach each other as going away from the movable mirror 22. The pair of levers 271, the first link member 272, the second link member 273, and the pair of beam members 274 define the light passage opening 25. The light passage opening 25 has a polygonal shape when viewed from the Z-axis direction. For example, the light passage opening 25 is a cavity (hole). Alternatively, a material having optical transparency with respect to the measurement light L0 and the laser light L10 may be disposed in the light passage opening 25.

The intermediate member 275 has a plate shape that extends along a plane perpendicular to the Z-axis direction, and extends in the Y-axis direction. The intermediate member 275 is disposed between the movable mirror 22 and the second link member 273 (in other words, between the movable mirror 22 and the light passage opening 25). The intermediate member 275 is connected to the movable mirror 22 through the non-linearity mitigation springs 278 as to be described later.

The pair of first torsion bars 276 respectively bridge the first end 271 d of one lever 271 and the base 21, and the first end 271 d of the other lever 271 and the base 21. That is, the pair of first torsion bars 276 are respectively connected between the pair of levers 271 and the base 21. The first torsion bars 276 extend in the Y-axis direction. The pair of first torsion bars 276 are disposed on the same central line parallel to the Y-axis direction. In this embodiment, the central line of the first torsion bars 276 and the central line of the first link member 272 are located on the same straight line. A protrusion 271 f that protrudes outward in the Y-axis direction is provided in each of the first ends 271 d of the levers 271, and each of the first torsion bars 276 is connected to the protrusion 271 f.

The pair of second torsion bars 277 respectively bridge the second end 271 e of one lever 271 and one end of the intermediate member 275, and the second end 271 e of the other lever 271 and the other end of the intermediate member 275. That is, the pair of second torsion bars 277 are respectively connected between the pair of levers 271 and the movable mirror 22. The respective second torsion bars 277 extend in the Y-axis direction. The pair of second torsion bars 277 are disposed on the same central line parallel to the Y-axis direction.

The pair of non-linearity mitigation springs 278 are connected between the movable mirror 22 and the intermediate member 275. That is, the pair of non-linearity mitigation springs 278 are connected between the movable mirror 22 and the second torsion bar 277. Each of the non-linearity mitigation springs 278 includes a meandering portion 278 a that extends in a meandering manner when viewed from the Z-axis direction. The meandering portion 278 a includes a plurality of straight portions 278 b which extend in the Y-axis direction and are aligned in the X-axis direction, and a plurality of folded portions 278 c which alternately connect both ends of the plurality of straight portions 278 b. One end of the meandering portion 278 a is connected to the intermediate member 275, and the other end of the meandering portion 278 a is connected to the frame portion 222. In the meandering portion 278 a, a portion on the frame portion 222 side has a shape along the outer edge of the frame portion 222.

The non-linearity mitigation spring 278 is constituted as follows. In a state in which the movable mirror 22 has moved in the Z-axis direction, the amount of deformation of the non-linearity mitigation spring 278 around the Y-axis direction becomes smaller than the amount of deformation of each of the first torsion bar 276 and the second torsion bar 277 around the Y-axis direction, and the amount of deformation of the non-linearity mitigation spring 278 in the X-axis direction becomes larger than the amount of deformation of each of the first torsion bar 276 and the second torsion bar 277 in the X-axis direction. Accordingly, it is possible to suppress occurrence of non-linearity in twist deformation of the first torsion bar 276 and the second torsion bar 277, and it is possible to suppress deterioration of control characteristics of the movable mirror 22 due to the non-linearity.

The plurality of electrode support portions 279 includes a pair of first electrode support portions 279 a, a pair of second electrode support portions 279 b, and a pair of third electrode support portions 279 c. Each of the electrode support portions 279 a, 279 b, and 279 c has a plate shape that extends along a plane perpendicular to the Z-axis direction, and extends in the Y-axis direction. Each of the electrode support portions 279 a, 279 b, and 279 c extends from the second portion 271 b of the lever 271 toward a side opposite to the light passage opening 25. The pair of first electrode support portions 279 a are disposed on the same central line parallel to the Y-axis direction. The pair of second electrode support portions 279 b are disposed on the same central line parallel to the Y-axis direction. The pair of third electrode support portions 279 c are disposed on the same central line parallel to the Y-axis direction. In the X-axis direction, the first electrode support portions 279 a, the second electrode support portions 279 b, and the third electrode support portions 279 c are aligned in this order from the movable mirror 22 side.

The actuator unit 28 moves the movable mirror 22 in the Z-axis direction. The actuator unit 28 includes a fixed comb-tooth electrode 281, a movable comb-tooth electrode 282, a fixed comb-tooth electrode 283, and a movable comb-tooth electrode 284. Positions of the fixed comb-tooth electrodes 281 and 283 are fixed. The movable comb-tooth electrodes 282 and 284 move in accordance with movement of the movable mirror 22.

The fixed comb-tooth electrode 281 is provided on a part of a surface, which faces the electrode support portions 269, of the device layer 102 of the base 21. The fixed comb-tooth electrode 281 includes a plurality of fixed comb-teeth 281 a which extend along a plane perpendicular to the Y-axis direction. The fixed comb-teeth 281 a are aligned in the Y-axis direction with a predetermined gap therebetween.

The movable comb-tooth electrode 282 is provided on a surface of each of the first electrode support portions 269 a on the movable mirror 22 side, on surfaces of each of the second electrode support portions 269 b on both sides in the X-axis direction, and on a surface of each of the third electrode support portion 269 c on the movable mirror 22 side. The movable comb-tooth electrode 282 includes a plurality of movable comb-teeth 282 a which extend along a plane perpendicular to the Y-axis direction. The movable comb-teeth 282 a are aligned in the Y-axis direction with a predetermined gap therebetween.

In the fixed comb-tooth electrode 281 and the movable comb-tooth electrode 282, the plurality of fixed comb-teeth 281 a and the plurality of movable comb-teeth 282 a are alternately arranged. That is, each of the fixed comb-teeth 281 a of the fixed comb-tooth electrode 281 is located between the movable comb-teeth 282 a of the movable comb-tooth electrode 282. The fixed comb-teeth 281 a and the movable comb-teeth. 282 a, which are adjacent to each other, face each other in the Y-axis direction. A distance between the fixed comb-tooth 281 a and the movable comb-tooth 282 a, which are adjacent to each other, is approximately several μm.

The fixed comb-tooth electrode 283 is provided on a part of a surface, which faces the electrode support portions 279, of the device layer 102 of the base 21. The fixed comb-tooth electrode 283 includes a plurality of fixed comb-teeth 283 a which extend along a plane perpendicular to the Y-axis direction. The fixed comb-teeth 283 a are aligned in the Y-axis direction with a predetermined gap therebetween.

The movable comb-tooth electrode 284 is provided on a surface of each of the first electrode support portion 279 a on the movable mirror 22 side, on surfaces of each of the second electrode support portions 279 b on both sides in the X-axis direction, and on a surface of each of the third electrode support portion 279 c on the movable mirror 22 side. The movable comb-tooth electrode 284 includes a plurality of movable comb-teeth 284 a which extend along a plane perpendicular to the Y-axis direction. The movable comb-teeth 284 a are aligned in the Y-axis direction with a predetermined gap therebetween.

In the fixed comb-tooth electrode 283 and the movable comb-tooth electrode 284, the plurality of fixed comb-teeth 283 a and the plurality of movable comb-teeth 284 a are alternately arranged. That is, each of the fixed comb-teeth 283 a of the fixed comb-tooth electrode 283 is located between the movable comb-teeth 284 a of the movable comb-tooth electrode 284. The fixed comb-teeth 283 a and the movable comb-teeth 284 a, which are adjacent to each other, face each other in the Y-axis direction. For example, a distance between the fixed comb-tooth 283 a and the movable comb-tooth 284 a, which are adjacent to each other, is approximately several μm.

A plurality of electrode pads 211 are provided in the base 21. The electrode pads 211 are disposed on a surface of the device layer 102 in an opening 213 formed in the first surface 21 a of the base 21 to reach the device layer 102. Some of the plurality of electrode pads 211 are electrically connected to the fixed comb-tooth electrode 281 or the fixed comb-tooth electrode 283 via the device layer 102. Several other electrode pads 211 among the plurality of electrode pads 211 are electrically connected to the movable comb-tooth electrode 282 or the movable comb-tooth electrode 284 via the first elastic support unit 26 or the second elastic support unit 27. In addition, a pair of electrode pads 212 which can be used as ground electrodes are provided in the base 21. The pair of electrode pads 212 are disposed on the first surface 21 a to be located on both sides of the movable mirror 22 in the Y-axis direction.

In the mirror device 20 configured as described above, an electric signal for moving the movable mirror 22 in the Z-axis direction, is input to the drive unit 23 through a lead pin 113 to be described later and a wire (not illustrated). Accordingly, for example, an electrostatic force is generated between the fixed comb-tooth electrode 281 and the movable comb-tooth electrode 282 which face each other, and the fixed comb-tooth electrode 283 and the movable comb-tooth electrode 284 which face each other so that the movable mirror 22 moves to one side in the Z-axis direction. At this time, the first torsion bars 266 and 276 and the second torsion bars 267 and 277 in the first elastic support unit 26 and the second elastic support unit 27 are twisted, and an elastic force is generated in the first elastic support unit 26 and the second elastic support unit 27. In the mirror device 20, when a periodic electric signal is applied to the drive unit 23, it is possible to reciprocate the movable mirror 22 in the Z-axis direction at a resonance frequency level. In this manner, the drive unit 23 functions as an electrostatic actuator.

As illustrated in FIG. 2, FIG. 3, FIG. 4, and FIG. 7, the optical function member 13 includes the third surface 13 a (a surface on the one side in the Z-axis direction) that faces the second surface 21 b of the base 21, and a fourth surface 13 b opposite to the third surface 13 a. The optical function member 13 is disposed on the other side in the Z-axis direction with respect to the mirror device 20. When viewed from the Z-axis direction, an outer edge 13 c of the optical function member 13 is located outside of an outer edge 21 c of the base 21. That is, when viewed from the Z-axis direction, the outer edge 13 c of the optical function member 13 surrounds the outer edge 21 c of the base 21. The optical function member 13 is integrally formed by a material having transparency with respect to the measurement light L0 and the laser light L10. For example, the optical function member 13 is formed in a rectangular plate shape by glass, and has a size of approximately 15 mm×20 mm×4 mm (thickness). For example, the material of the optical function member 13 is selected in accordance with a sensitivity wavelength of the optical module 1A. For example, the material is set to glass in a case where the sensitivity wavelength of the optical module 1A is a near infrared region, and the material is set to silicon in a case where the sensitivity wavelength of the optical module 1A is an intermediate infrared region.

A pair of light transmitting portions 14 and 15 are provided in the optical function member 13. The light transmitting portion 14 is a portion, which faces the light passage opening 24 of the mirror device 20 in the Z-axis direction, in the optical function member 13. The light transmitting portion 15 is a portion, which faces the light passage opening 25 of the mirror device 20 in the Z-axis direction, in the optical function member 13. A surface 14 a of the light transmitting portion 14 on the mirror device 20 side, and a surface 15 a of the light transmitting portion 15 on the mirror device 20 side are located on the same plane as the third surface 13 a. The light transmitting portion (second light passage portion) 14 constitutes a second portion (partial portion) of an optical path between the beam splitter unit 3 and the fixed mirror 16. The light transmitting portion 14 is a portion that corrects an optical path difference that occurs between an optical path between the beam splitter unit 3 and the movable mirror 22, and an optical path between the beam splitter unit 3 and the fixed mirror 16. In this embodiment, the light transmitting portion 15 does not function as a light transmitting portion.

The optical function member 13 includes a fifth surface 13 d that faces the movable mirror 22 and the drive unit 23 of the mirror device 20. The fifth surface 13 d is located on the fourth surface 13 b side in comparison to the third surface 13 a. The fifth surface 13 d extends to the outer edge 13 c of the optical function member 13 when viewed from the Z-axis direction. In this embodiment, the fifth surface 13 d extends to a pair of opposite sides which extend in the Y-axis direction in the outer edge 13 c of the optical function member 13 while surrounding ends of the respective light transmitting portions 14 and 15 on the mirror device 20 side.

The third surface 13 a of the optical function member 13 is joined to the second surface 21 b of the base 21 by direct bonding (for example, plasma activation bonding, surface-activated room-temperature bonding (SAB), atomic diffusion bonding (ADB), anodic bonding, fusion bonding, hydrophilic bonding, and the like). In this embodiment, the third surface 13 a extends to face a plurality of the electrode pads 211 and 212 provided in the base 21 on both sides of the fifth surface 13 d in the Y-axis direction. Here, the fifth surface 13 d is located on the fourth surface 13 b side in comparison to the third surface 13 a, and thus the fifth surface 13 d is separated from the mirror device 20 in a region where the fifth surface 13 d faces the movable mirror 22 and the drive unit 23. In addition, the surface 14 a of the light transmitting portion 14 and the surface 15 a of the light transmitting portion 15 respectively face the light passage openings 24 and 25 of the mirror device 20. Accordingly, in the mirror unit 2, when the movable mirror 22 reciprocates in the Z-axis direction, the movable mirror 22 and the drive unit 23 are prevented from coming into contact with the optical function member 13.

A sixth surface 21 d, which is separated from the optical function member 13 in a state in which the third surface 13 a of the optical function member 13 and the second surface 21 b of the base 21 are joined to each other, is provided in the base 21 of the mirror device 20. The sixth surface 21 d is separated from the optical function member 13 in a region that includes at least a part of an outer edge of the base 21 when viewed from the Z-axis direction. In this embodiment, the sixth surface 21 d is formed by removing the device layer 102 and the intermediate layer 103 along one side, which extends in the Y-axis direction, in the outer edge of the base 21 by etching. In addition, a plurality of reference holes 13 e are formed in the third surface 13 a of the optical function member 13. In this embodiment, the plurality of reference holes 13 e are formed in the third surface 13 a to correspond to a plurality of corners of the base 21. When the third surface 13 a of the optical function member 13 and the second surface 21 b of the base 21 are joined to each other, handling of the mirror device 20 is performed in a state in which a portion of the base 21 which corresponds to the sixth surface 21 d is gripped, and thus a position of the mirror device 20 in the X-axis direction and the Y-axis direction, and an angle of the mirror device 20 in a plane perpendicular to the Z-axis direction are adjusted based on the plurality of reference holes 13 e.

As illustrated in FIG. 3 and FIG. 4, the fixed mirror 16 is disposed on the other side (side opposite to the mirror device 20) in the Z-axis direction with respect to the optical function member 13, and a position of the mirror device 20 with respect to the base 21 is fixed. For example, the fixed mirror 16 is formed on the fourth surface 13 b of the optical function member 13 by vapor deposition. The fixed mirror 16 includes a mirror surface 16 a perpendicular to the Z-axis direction. In this embodiment, the mirror surface 22 a of the movable mirror 22, and the mirror surface 16 a of the fixed mirror 16 face one side (beam splitter unit 3 side) in the Z-axis direction. The fixed mirror 16 is formed continuously with the fourth surface 13 b of the optical function member 13 to reflect light that is transmitted through the respective light transmitting portions 14 and 15 of the optical function member 13. However, a fixed mirror that reflects light transmitted through the light transmitting portion 14, and a fixed mirror that reflects light transmitted through the light transmitting portion 15 may be provided, respectively.

The stress mitigation substrate 17 is attached to the fourth surface 13 b of the optical function member 13 via the fixed mirror 16. For example, the stress mitigation substrate 17 is attached to the fixed mirror 16, for example, by an adhesive. When viewed from the Z-axis direction, an outer edge of the stress mitigation substrate 17 is located outside of the outer edge 13 c of the optical function member 13. That is, when viewed from the Z-axis direction, the outer edge of the stress mitigation substrate 17 surrounds the outer edge 13 c of the optical function member 13. A thermal expansion coefficient of the stress mitigation substrate 17 is closer to a thermal expansion coefficient of the base 21 of the mirror device 20 (more specifically, a thermal expansion coefficient of the support layer 101) in comparison to a thermal expansion coefficient of the optical function member 13. In addition, the thickness of the stress mitigation substrate 17 is closer to the thickness of the base 21 of the mirror device 20 in comparison to the thickness of the optical function member 13. For example, the stress mitigation substrate 17 is formed in a rectangular plate shape by silicon, and has a size of approximately 16 mm×21 mm×0.65 mm (thickness).

As illustrated in FIG. 1, the mirror unit 2 configured as described above is attached to the support 9 by fixing a surface of the stress mitigation substrate 17 on a side opposite to the optical function member 13 to a surface 9 a of the support 9 (surface on the one side in the Z-axis direction), for example, by an adhesive. When the mirror unit 2 is attached to the support 9, as illustrated in FIG. 8, a position of the mirror device 20 in the X-axis direction and the Y-axis direction and an angle of the mirror device 20 in a plane perpendicular to the Z-axis direction are adjusted based on a reference hole 9 b that is formed in the support 9. In FIG. 8, the second support structure 12 is not illustrated.

[Configuration of First Support Structure and Beam Splitter Unit]

As illustrated in FIG. 1 and FIG. 8, the first support structure 11 includes a frame body 111, a light transmitting member 112, and a plurality of lead pins 113. The frame body 111 is formed so as to surround the mirror unit 2 when viewed from the Z-axis direction, and is attached to the surface 9 a of the support 9, for example, by an adhesive such as silver solder. For example, the frame body 111 is formed of ceramic, and has a rectangular frame shape. An end surface 111 a of the frame body 111 on a side opposite to the support 9 is located on a side opposite to the support 9 in comparison to the first surface 21 a of the base 21 of the mirror device 20.

The light transmitting member 112 is formed so as to close an opening of the frame body 111, and is attached to the end surface 111 a of the frame body 111, for example, by an adhesive. The light transmitting member 112 is formed of a material having transparency with respect to the measurement light L0 and the laser light L10, and has, for example, a rectangular plate shape. Here, the end surface 111 a of the frame body 111 is located on a side opposite to the support 9 in comparison to the first surface 21 a of the base 21 of the mirror device 20, and thus the light transmitting member 112 is separated from the mirror device 20. Accordingly, in the optical module 1A, when the movable mirror 22 reciprocates in the Z-axis direction, the movable mirror 22 and the drive unit 23 are prevented from coming into contact with the light transmitting member 112. In the optical module 1A, the support 9, the frame body 111, and the light transmitting member 112 constitute a package that accommodates the mirror unit 2.

The lead pins 113 are provided in the frame body 111 in such a manner that one end 113 a is located inside the frame body 111, and the other end (not illustrated) is located outside the frame body 111. The one end 113 a of each of the lead pins 113 is electrically connected to the electrode pad 211 or 212 corresponding to the lead pin 113 in the mirror device 20 by a wire (not illustrated). In the optical module 1A, an electric signal for moving the movable mirror 22 in the Z-axis direction is input to the drive unit 23 through a plurality of lead pins 113. In this embodiment, a stepped surface 111 b that extends in the X-axis direction on both sides of the optical function member 13 in the Y-axis direction is formed in the frame body 111, and the one end 113 a of the lead pin 113 is disposed on the stepped surface 111 b. The lead pin 113 extends in the Z-axis direction on both sides of the support 9 in the Y-axis direction, and the other end of the lead pin 113 is located on the other side in the Z-axis direction in comparison to the support 9.

As illustrated in FIG. 10, the beam splitter unit 3 is attached to a surface 112 a on a side opposite to the mirror device 20 in the light transmitting member 112, for example, by an optical adhesive that also functions as a refractive index matching agent. The beam splitter unit 3 includes a first mirror surface 31, a second mirror surface 32, and a plurality of optical surfaces 33 a, 33 b, 33 c, and 33 d. The beam splitter unit 3 is constituted by joining a plurality of optical blocks 34, 35, and 36. The optical blocks 34, 35, and 36 are formed of a material having a refractive index that is the same as or similar to that of the optical function member 13. FIG. 10 is a schematic cross-sectional view of the mirror unit 2 and the beam splitter unit 3 illustrated in FIG. 1, and in FIG. 10, the mirror device 20 is schematically illustrated, for example, in a state in which dimensions in the Z-axis direction are enlarged in comparison to actual dimensions.

The first mirror surface 31 is a mirror surface (for example, a half mirror surface) that is inclined with respect to the Z-axis direction, and is formed between the optical block 34 and the optical block 35. In this embodiment, the first mirror surface 31 is a surface that is parallel to the Y-axis direction and has an angle of 45° with respect to the Z-axis direction, and is inclined to be spaced away from the light incident unit 4 as it approaches the mirror device 20. The first mirror surface 31 has a function of reflecting a part of the measurement light L0 and allowing the remainder of the measurement light L0 to be transmitted therethrough, and a function of reflecting a part of the laser light L10 and allowing the remainder of the laser light L10 to be transmitted therethrough. For example, the first mirror surface 31 is formed of a dielectric multi-layer film. The first mirror surface 31 overlaps the light passage portion 24 of the mirror device 20, the light transmitting portion 14 of the optical function member 13, and the mirror surface 16 a of the fixed mirror 16 when viewed from the Z-axis direction, and overlaps the light incident unit 4 when viewed from the X-axis direction (refer to FIG. 1). That is, the first mirror surface 31 faces the fixed mirror 16 in the Z-axis direction, and faces the light incident unit 4 in the X-axis direction.

The second mirror surface 32 is a mirror surface (for example, a total reflection mirror surface) that is parallel to the first mirror surface 31, and is formed in the optical block 36 to be located on a side opposite to the light incident unit 4 with respect to the first mirror surface 31. The second mirror surface 32 has a function of reflecting the measurement light L0 and a function of reflecting the laser light L10. For example, the second mirror surface 32 is formed of a metal film. The second mirror surface 32 overlaps the mirror surface 22 a of the movable mirror 22 of the mirror device 20 when viewed from the Z-axis direction, and overlaps the first mirror surface 31 when viewed from the X-axis direction. That is, the second mirror surface 32 faces the movable mirror 22 in the Z-axis direction, and faces the first mirror surface 31 in the X-axis direction.

The optical surface 33 a is a surface that is perpendicular to the Z-axis direction, and is formed in the optical block 35 to be located on a side opposite to the mirror device 20 with respect to the first mirror surface 31. The optical surface 33 b is a surface that is perpendicular to the Z-axis direction, and is formed in the optical block 36 to be located on the mirror device 20 side with respect to the second mirror surface 32. The optical surface 33 c is a surface that is perpendicular to the Z-axis direction, and is formed in the optical block 34 to be located on the mirror device 20 side with respect to the first mirror surface 31. The optical surface 33 b and the optical surface 33 c are located on the same plane. The optical surface 33 d is a surface that is perpendicular to the X-axis direction, and is formed in the optical block 34 to be located on the light incident unit 4 side with respect to the first mirror surface 31. The optical surfaces 33 a, 33 b, 33 c, and 33 d have a function of allowing the measurement light L0 to be transmitted therethrough and a function of allowing the laser light L10 to be transmitted therethrough.

The beam splitter unit 3 configured as described above is attached to the light transmitting member 112 by fixing the optical surface 33 b and the optical surface 33 c which are located on the same plane to the surface 112 a of the light transmitting member 112, for example, by an optical adhesive. When the beam splitter unit 3 is attached to the light transmitting member 112, as illustrated in FIG. 9, a position of the beam splitter unit 3 in the X-axis direction and the Y-axis direction, and an angle of the beam splitter unit 3 in a plane perpendicular to the Z-axis direction are adjusted based on the reference hole 9 b formed in the support 9. In FIG. 9, the second support structure 12 is not illustrated.

Here, the optical path of the measurement light L0 and the optical path of the laser light L10 in the mirror unit 2 and the beam splitter unit 3 will be described in detail with reference to FIG. 10.

As illustrated in FIG. 10, when the measurement light L0 is incident to the beam splitter unit 3 in the X-axis direction through the optical surface 33 d, a part of the measurement light L0 is transmitted through the first mirror surface 31, is reflected by the second mirror surface 32, and reaches the mirror surface 22 a of the movable mirror 22 through the optical surface 33 b and the light transmitting member 112. The part of the measurement light L0 is reflected by the mirror surface 22 a of the movable mirror 22, and proceeds on the same optical path P1 in an opposite direction, and is reflected by the first mirror surface 31. The remainder of the measurement light L0 is reflected by the first mirror surface 31, and reaches the mirror surface 16 a of the fixed mirror 16 through the optical surface 33 c, the light transmitting member 112, the light passage opening 24 of the mirror device 20, and the light transmitting portion 14 of the optical function member 13. The remainder of the measurement light L0 is reflected by the mirror surface 16 a of the fixed mirror 16, proceeds on the same optical path P2 in an opposite direction, and is transmitted through the first mirror surface 31. The part of the measurement light L0 which is reflected by the first mirror surface 31, and the remainder of the measurement light L0 which is transmitted through the first mirror surface 31 become interference light L1, and the interference light L1 of the measurement light is emitted from the beam splitter unit 3 through the optical surface 33 a along the Z-axis direction.

On the other hand, when the laser light L10 is incident to the beam splitter unit 3 in the Z-axis direction through the optical surface 33 a, a part of the laser light L10 is reflected by the first mirror surface 31 and the second mirror surface 32, and reaches the mirror surface 22 a of the movable mirror 22 through the optical surface 33 b and the light transmitting member 112. The part of the laser light L10 is reflected by the mirror surface 22 a of the movable mirror 22, proceeds on the same optical path P3 in an opposite direction, and is reflected by the first mirror surface 31. The remainder of the laser light L10 is transmitted through the first mirror surface 31, and reaches the mirror surface 16 a of the fixed mirror 16 through the optical surface 33 c, the light transmitting member 112, the light passage opening 24 of the mirror device 20, and the light transmitting portion 14 of the optical function member 13. The remainder of the laser light L10 is reflected by the mirror surface 16 a of the fixed mirror 16, proceeds on the same optical path P4 in an opposite direction, and is transmitted through the first mirror surface 31. The part of the laser light L10 which is reflected by the first mirror surface 31, and the remainder of the laser light L10 which is transmitted through the first mirror surface 31 become interference light L11, and the interference light L11 of the laser light is emitted from the beam splitter unit 3 through the optical surface 33 a along the Z-axis direction.

As described above, the light passage opening 24 of the mirror device 20 constitutes a first portion P2 a of the optical path P2 of the measurement light L0 and a first portion P4 a of the optical path P4 of the laser light L10 in an optical path between the beam splitter unit 3 and the fixed mirror 16. In addition, the light transmitting portion 14 of the optical function member 13 constitutes a second portion P2 b of the optical path P2 of the measurement light L0 and a second portion P4 b of the optical path P4 of the laser light L10 in the optical path between the beam splitter unit 3 and the fixed mirror 16.

The second portion P2 b of the optical path P2 of the measurement light L0 is constituted by the light transmitting portion 14, thus an optical path difference between both the optical paths P1 and P2 is corrected so that a difference between an optical path length (optical path length in consideration of a refractive index of respective media through which the optical path passes) of the optical path P1 of the measurement light L0, and an optical path length of the optical path P2 of the measurement light L0 decreases. Similarly, the second portion P4 b of the optical path P4 of the laser light L10 is constituted by the light transmitting portion 14, thus an optical path difference between both the optical paths P3 and P4 is corrected so that a difference between an optical path length of the optical path P3 of the laser light L10 and an optical path length of the optical path P4 of the laser light L10 decreases. In this embodiment, a refractive index of the light transmitting portion 14 is the same as a refractive index of the respective optical blocks which constitute the beam splitter unit 3, and a distance between the first mirror surface 31 and the second mirror surface 32 in the X-axis direction is the same as the thickness of the light transmitting portion 14 in the Z-axis direction (that is, a distance between the surface 14 a of the light transmitting portion 14 and the fourth surface 13 b of the optical function member 13 in the Z-axis direction).

[Configuration of Second Support Structure, Light Incident Unit, and the Like]

As illustrated in FIG. 1, the second support structure 12 includes a connection unit 120. The connection unit 120 includes a main body portion 121, a frame body 122, and a fixing plate 123. The main body portion 121 includes a pair of side wall portions 124 and 125, and a ceiling wall portion 126. The pair of side wall portions 124 and 125 face each other in the X-axis direction. An opening 124 a is formed in the side wall portion 124 on one side in the X-axis direction. The ceiling wall portion 126 faces the support 9 in the Z-axis direction. An opening 126 a is formed in the ceiling wall portion 126. For example, the main body portion 121 is integrally formed of a metal. Positioning pins 121 a are provided in the main body portion 121. The main body portion 121 is positioned with respect to the support 9 by inserting the positioning pin 121 a into the reference hole 9 b formed in the support 9, and is attached to the support 9 in this state, for example, by a bolt.

The frame body 122 is disposed on a surface of the side wall portion 124 on a side opposite to the beam splitter unit 3. An opening of the frame body 122 faces the beam splitter unit 3 through the opening 124 a of the side wall portion 124. The light incident unit 4 is disposed in the frame body 122. The fixing plate 123 is a member that fixes the light incident unit 4 disposed in the frame body 122 to the main body portion 121 (details will be described later).

The light incident unit 4 includes a holder 41 and a collimator lens 42. The holder 41 holds the collimator lens 42, and is configured so that an optical fiber (not illustrated) that guides the measurement light L0 can be connected to the holder 41. The collimator lens 42 collimates the measurement light L0 emitted from the optical fiber. When the optical fiber is connected to the holder 41, an optical axis of the optical fiber matches an optical axis of the collimator lens 42.

A flange portion 41 a is provided in the holder 41. The flange portion 41 a is disposed between the frame body 122 and the fixing plate 123. In this state, fixing plate 123 is attached to the side wall portion 124, for example, by a bolt, and the light incident unit 4 disposed in the frame body 122 is fixed to the main body portion 121. In this manner, the light incident unit 4 is disposed on one side of the beam splitter unit 3 in the X-axis direction, and is supported by the second support structure 12. The light incident unit 4 allows measurement light L0 that is incident from the first light source through a measurement target or measurement light L0 that is generated from the measurement target (in this embodiment, the measurement light L0 guided by the optical fiber) to be incident to the beam splitter unit 3.

A filter (second filter) 54 is attached to the frame body 122. The filter 54 has a function of allowing the measurement light L0 to be transmitted therethrough and cutting off the laser light L10. For example, the filter 54 is formed in a plate shape with silicon. The filter 54 is disposed in the opening 124 a of the side wall portion 124 in a state of being inclined with respect to an optical axis of the light incident unit 4. The filter 54 closes the opening of the frame body 122 when viewed from the X-axis direction. In this manner, the filter 54 is disposed between the light incident unit 4 and the beam splitter unit 3 (that is, on the light incident unit 4 side with respect to the beam splitter unit 3), and is supported by the second support structure 12 in a state of being inclined with respect to an optical axis of the light incident unit 4. In this embodiment, an optical surface of the filter 54 is a surface that is parallel to the Z-axis direction, and has an angle of 10° to 20° with respect to the Y-axis direction. However, the angle between the optical surface of the filter 54 between an optical axis of the measurement light L0 is not limited to 10° to 20°, and may be other angles. The optical axis of the light incident unit 4 is parallel to the X-axis direction.

In this embodiment, the filter 54 has a function of allowing the measurement light L0 to be transmitted therethrough, and absorbing the laser light L10. That is, in the filter 54, a transmittance of the measurement light L0 becomes higher than a transmittance of the laser light L10, and an absorptance of the laser light L10 becomes higher than an absorptance of the measurement light L0. In this embodiment, the filter 54 has the function of absorbing the laser light L10 as the function of cutting off the laser light L10, but may have a function of reflecting the laser light L10, for example, to the outside of the interference optical system as the function of cutting off the laser light L10. In this case, in the filter 54, the transmittance of the measurement light L0 becomes higher than the transmittance of the laser light L10, and a reflectance of the laser light L10 becomes higher than a reflectance of the measurement light L0.

The second support structure 12 further includes a holding unit 130. The holding unit 130 includes a main body portion 131. The main body portion 131 is attached to a surface of the ceiling wall portion 126 on a side opposite to the support 9. The main body portion 131 is positioned with respect to the main body portion 121 of the connection unit 120 by a plurality of positioning pins 131 a, and in this state, the main body portion 131 is attached to the ceiling wall portion 126, for example, by a bolt. A first through-hole 135, a second through-hole 136, and a third through-hole 137 are formed in the main body portion 131. Each of the first through-hole 135, the second through-hole 136, and the third through-hole 137 passes through the main body portion 131 along the Z-axis direction. The first through-hole 135 is formed at a position that faces the first mirror surface 31 of the beam splitter unit 3 in the Z-axis direction. The second through-hole 136 is formed on the other side of the first through-hole 135 in the X-axis direction (that is, on a site opposite to the light incident unit 4). The third through-hole 137 is formed on the other side of the second through-hole 136 in the X-axis direction.

The first light detector 6 is disposed in the first through-hole 135. The first light detector 6 includes a light detection element 62, a package 64 including a light transmission window 64 a, a holder 61, and a condensing lens 63. The package 64 accommodates the light detection element 62. The light detection element 62 detects the interference light L1 of the measurement light. For example, the light detection element 62 is an InGaAs photodiode. The holder 61 holds the package 64 and the condensing lens 63. The condensing lens 63 condenses the interference light L1 of the measurement light which is incident to the light detection element 62 through the light transmission window 64 a to the light detection element 62. An optical axis of the light detection element 62 and an optical axis of the condensing lens 63 match each other.

The holder 61 is provided with a flange portion 61 a. The flange portion 61 a positioned with respect to the main body portion 121 of the connection unit 120 by a positioning pin 61 b, and in this state, the flange portion 61 a is attached to the ceiling wall portion 126 of the main body portion 121, for example, by a bolt. In this manner, the first light detector 6 is disposed on one side of the beam splitter unit 3 in the Z-axis direction, and is supported by the second support structure 12. The first light detector 6 faces the first mirror surface 31 of the beam splitter unit 3 in the Z-axis direction. The first light detector 6 detects interference light L1 of the measurement light which is emitted from the beam splitter unit 3.

The second light detector 8 is disposed in the second through-hole 136. The second light detector 8 includes a light detection element 82, and a package 84 including a condensing lens 84 a. The light detection element 82 detects interference light L1 of the laser light. For example, the light detection element 82 is a Si photodiode. The condensing lens 84 a condenses the interference light L11 of the laser light which is incident to the light detection element 82 to the light detection element 82. An optical axis of the light detection element 82 and an optical axis of the condensing lens 84 a match each other.

The package 84 is fixed to the main body portion 131 in the second through-hole 136. In this manner, the second light detector 8 is disposed on the other side of the first light detector 6 in the X-axis direction (on one side of the first optical device in a direction intersecting an optical axis of the first optical device) to face the same side as in the first light detector 6, and is supported by the second support structure 12. The second light detector 8 detects interference light L11 of the laser light which is emitted from the beam splitter unit 3.

The second light source 7 is disposed in the third through-hole 137. The second light source 7 includes a light-emitting element 72, and a package 74 including a collimator lens 74 a. The light-emitting element 72 emits the laser light L10. For example, the light-emitting element 72 is a semiconductor laser such as VCSEL. The collimator lens 74 a collimates the laser light L10 emitted from the light-emitting element 72. An optical axis of the light-emitting element 72 and an optical axis of the collimator lens 74 a match each other.

The package 74 is fixed to the main body portion 131 in the third through-hole 137. In this manner, the second light source 7 is disposed on the other side of the second light detector 8 in the X-axis direction (on one side of the second optical device in a direction intersecting the optical axis of the first optical device) to face the same side as in the first light detector 6, and is supported by the second support structure 12. The second light source 7 emits the laser light L0 to be incident to the beam splitter unit 3.

As described above, the holding unit 130 holds the first light detector 6, the second light detector 8, and the second light source 7 so that the first light detector (first optical device) 6, the second light detector (second optical device) 8, and the second light source (third optical device) 7 face the same side, and the first light detector 6, the second light detector 8, and the second light source 7 are aligned in this order. In this embodiment, on one side of the beam splitter unit 3 in the Z-axis direction, the holding unit 130 holds the first light detector 6, the second light detector 8, and the second light source 7 so that the first light detector 6, the second light detector 8, and the second light source 7 face the other side (that is, the beam splitter unit 3 side). In addition, the holding unit 130 holds the first light detector 6, the second light detector 8, and the second light source 7 so that the first light detector 6, the second light detector 8, and the second light source 7 are aligned in this order from one side (that is, the light incident unit 4 side) in the X-axis direction.

A configuration in which the first light detector 6 faces an arbitrary side represents that a light-receiving surface of the light detection element 62 faces the arbitrary side (that is, the first light detector 6 is disposed to detect light incident from the arbitrary side). In this case, for example, a lead pin of the light detection element 62 extends to a side opposite to the arbitrary side. Similarly, a configuration in which the second light detector 8 faces an arbitrary side represents that a light-receiving surface of the light detection element 82 faces the arbitrary side (that is, the second light detector 8 is disposed to detect light incident from the arbitrary side). In this case, for example, a lead pin of the light detection element 82 extends to a side opposite to the arbitrary side. In addition, a configuration in which the second light source 7 faces an arbitrary side represents that a light emission surface of the light-emitting element 72 faces the arbitrary side (that is, the second light source 7 is disposed to emit light to the arbitrary side). In this case, for example, a lead pin of the light-emitting element 72 extends to a side opposite to the arbitrary side. In addition, the holding unit 130 is a part of the second support structure 12, and thus a configuration in which the holding unit 130 holds an arbitrary constituent element represents that the arbitrary constituent element is supported by the second support structure 12.

A first mirror 51, a second mirror 52, and a third mirror 53 are attached to the main body portion 121 of the connection unit 120. The first mirror 51 is attached to the ceiling wall portion 126 of the main body portion 121 in the opening 126 a to be located on a side opposite to the first light detector 6 with respect to the first through-hole 135. The second mirror 52 is attached to the ceiling wall portion 126 of the main body portion 121 in the opening 126 a to be located on a side opposite to the second light detector 8 with respect to the second through-hole 136. The third mirror 53 is attached to the ceiling wall portion 126 of the main body portion 121 in the opening 126 a to be located on a side opposite to the second light source 7 with respect to the third through-hole 137.

The first mirror 51 is a dichroic mirror that has a function of allowing the measurement light L0 to be transmitted therethrough and of reflecting the laser light L10, and is inclined with respect to the optical axis of the first light detector 6. The first mirror 51 is disposed between the beam splitter unit 3 and the first light detector 6. That is, the first mirror 51 is disposed to face the beam splitter unit 3 and the first light detector 6. In this embodiment, an optical surface of the first mirror 51 is a surface that is parallel to the Y-axis direction and has an angle of 45° with respect to the Z-axis direction. The optical axis of the first light detector 6 is parallel to the Z-axis direction.

The second mirror 52 is a mirror (for example, a half mirror) that has a function of reflecting a part of the laser light L10 and allowing the remainder of the laser light L10 to be transmitted therethrough, and is parallel to the first mirror 51. The second mirror 52 is disposed to overlap the first mirror 51 when viewed from the X-axis direction, and to overlap the second light detector 8 when viewed from the Z-axis direction. That is, the second mirror 52 is disposed to face the first mirror 51 and the second light detector 8. In this embodiment, an optical surface of the second mirror 52 is a surface that is parallel to the Y-axis direction, and has an angle of 45° with respect to the Z-axis direction.

The third mirror 53 is a mirror (for example, a total reflection mirror) that has a function of reflecting the laser light L0 and is parallel to the second mirror 52. The third mirror 53 is disposed to overlap the second mirror 52 when viewed from the X-axis direction, and overlap the second light source 7 when viewed from the Z-axis direction. That is, the third mirror 53 is disposed to face the second mirror 52 and the second light source 7. In this embodiment, an optical surface of the third mirror 53 is a surface that is parallel to the Y-axis direction, and has an angle of 45° with respect to the Z-axis direction.

A filter (first filter) 56 is disposed between the first mirror 51 and the first light detector 6. An aperture 55 is disposed between the first mirror 51 and the filter 56. In this embodiment, the aperture 55 and the filter 56 are held by the holder 61 of the first light detector 6. The aperture 55 is a member in which an opening having a circular shape is formed when viewed from the Z-axis direction. The filter 56 has a function of allowing the measurement light L0 to be transmitted therethrough and cutting off the laser light L10. In this embodiment, the filter 56 is a member different from a member in which the first mirror 51 is formed on a surface on the beam splitter unit 3 side (on a surface facing the beam splitter unit 3). More specifically, for example, the filter 56 is a silicon plate in which an anti-reflection film is formed on a light incident surface. In this embodiment, the filter 56 is a member different from the member in which the first mirror 51 is formed, and thus the degree of freedom of design of the first mirror 51 and the filter 56 is improved.

In this embodiment, the filter 56 has a function of allowing the measurement light L0 to be transmitted therethrough and absorbing the laser light L10. That is, in the filter 56, a transmittance of the measurement light L0 becomes higher than a transmittance of the laser light L10, and an absorbance of the laser light L10 becomes higher than an absorbance of the measurement light L0. In this embodiment, the filter 56 has the function of absorbing the laser light L10 as the function of cutting off the laser light L10, but may have a function of reflecting the laser light L10, for example, to the outside of the interference optical system as the function of cutting off the laser light L10. In this case, in the filter 56, the transmittance of the measurement light L0 becomes higher than the transmittance of the laser light L10, and a reflectance of the laser light L10 becomes higher than a reflectance of the measurement light L0.

A return light suppressing unit 57 is disposed on a side opposite to the second light detector 8 with respect to the second mirror 52. The return light suppressing unit 57 has a function of suppressing incident laser light L10 from becoming return light (that is, suppressing the laser light L0 from being reflected along an optical path of the incident laser light L10). In this embodiment, the return light suppressing unit 57 has a function of absorbing the incident laser light L10. In this embodiment, the return light suppressing unit 57 is apart of the second support structure (support) 12 that supports the second mirror 52. More specifically, the return light suppressing unit 57 is a portion that protrudes from the side wall portion 125 of the main body portion 121 of the connection unit 120 to the beam splitter unit 3 side. The return light suppressing unit 57 is constituted by forming a black resist layer on the portion, or by performing a black almite treatment to the portion. In this embodiment, the return light suppressing unit 57 is a part of the second support structure 12, and thus an increase of the number of parts is suppressed. In this embodiment, the return light suppressing unit 57 has the function of absorbing the incident laser light L10 as the function of suppressing the incident laser light L10 from becoming return light, but may have a function of reflecting the incident laser light L10, for example, to the outside of the interference optical system as the function of suppressing the incident laser light L10 from becoming return light.

Here, description will be given of an optical path between the beam splitter unit 3 and the first light detector 6, and the like. The interference light L1 of the measurement light which is emitted from the beam splitter unit 3 along the Z-axis direction is transmitted through the first mirror 51, is incident to the first light detector 6 through the aperture 55 and the filter 56, and is detected by the first light detector 6. On the other hand, the laser light L10 emitted from the second light source 7 is reflected by the third mirror 53, is transmitted through the second mirror 52, is reflected by the first mirror 51, and is incident to the beam splitter unit 3 along the Z-axis direction. Interference light L ii of the laser light which is emitted from the beam splitter unit 3 along the Z-axis direction is reflected by the first mirror 51 and the second mirror 52, and is incident to the second light detector 8 and is detected by the second light detector 8. A part of the laser light L10 reflected by the second mirror 52 is suppressed from becoming return light due to the return light suppressing unit 57.

In the optical module 1A, a length of the optical path between the beam splitter unit 3 and the first light detector 6 is shorter than a length of an optical path between the beam splitter unit 3 and the second light detector 8, and is shorter than a length of an optical path between the beam splitter unit 3 and the second light source 7. The lengths of the optical paths represent physical distances along the optical paths.

Specifically, a distance from an intersection between the optical path and the first mirror surface 31 of the beam splitter unit 3 to a light incident surface of the first light detector 6 is shorter than a distance from an intersection between an optical path and the first mirror surface 31 of the beam splitter unit 3 to a light incident surface of the second light detector 8, and is shorter than a distance from an intersection between an optical path and the first mirror surface 31 of the beam splitter unit 3 to a light emission surface of the second light source 7. A distance from an intersection between an optical path and the first mirror surface 31 of the beam splitter unit 3 to a light incident surface of the condensing lens 63 of the first light detector 6 is shorter than a distance from an intersection between an optical path and the first mirror surface 31 of the beam splitter unit 3 to a light incident surface of the condensing lens 84 a of the second light detector 8, and is shorter than a distance from an intersection between an optical path and the first mirror surface 31 of the beam splitter unit 3 to a light emission surface of the collimator lens 74 a of the second light source 7. A distance from the optical surface 33 a of the beam splitter unit 3 to the light incident surface of the first light detector 6 is shorter than a distance from the optical surface 33 a of the beam splitter unit 3 to the light incident surface of the second light detector 8, and is shorter than a distance from the optical surface 33 a of the beam splitter unit 3 to the light emission surface of the second light source 7. A distance from the optical surface 33 a of the beam splitter unit 3 to the light incident surface of the condensing lens 63 of the first light detector 6 is shorter than a distance from optical surface 33 a of the beam splitter unit 3 to the light incident surface of the condensing lens 84 a of the second light detector 8, and is shorter than a distance from the optical surface 33 a of the beam splitter unit 3 to the light emission surface of the collimator lens 74 a of the second light source 7.

In this embodiment, the light incident unit 4 has a configuration in which angle adjustment of the holder 41 with respect to the frame body 122 is possible. In contrast, the first light detector 6 is fixed to the ceiling wall portion 126 of the main body portion 121, for example, by a bolt in a state of being positioned with respect to the main body portion 121 of the connection unit 120. Accordingly, in a state in which the first light detector 6 is positioned, the angle adjustment of the holder 41 can be carried out so that detection intensity in the first light detector 6 becomes the maximum while the measurement light L0 is incident to the beam splitter unit 3. In addition, in a state in which the angle adjustment is carried out, the light incident unit 4 can be fixed to the frame body 122.

Not only the light incident unit 4 but also the first light detector 6 may have a configuration in which angle adjustment of the holder 61 is possible. In addition, the second light source 7 may have a configuration in which angle adjustment is possible in a state in which the second light detector 8 is positioned. In addition, not only the second light source 7 but also the second light detector 8 may have a configuration in which the angle adjustment is possible.

[Operation and Effect]

In the optical module 1A, the first light detector 6, the second light detector 8, and the second light source 7 are disposed to face the same side. Accordingly, it is possible to constitute the interference optical system relating to the measurement light L0 and the interference optical system relating to the laser light L10 with a simple layout, and it is possible to carry out spectral analysis on the basis of a detection result of the interference light L1 of the measurement light while acquiring a position of the movable mirror 22 in the Z-axis direction on the basis of a detection result of the interference light L1 of the laser light. In addition, the return light suppressing unit 57 having a function of suppressing incident laser light L10 from becoming return light is disposed on a side opposite to the second light detector 8 with respect to the second mirror 52. Accordingly, it is possible to prevent a component other than a component reflected by each of the movable mirror 22 and the fixed mirror 16 from being superimposed on the interference light L11 of the laser light, and thus it is possible to acquire a position of the movable mirror 22 in the Z-axis direction with accuracy. In addition, the first light detector 6, the second light detector 8, and the second light source 7 are disposed to be aligned in this order. Accordingly, it is possible to shorten a length of an optical path between the beam splitter unit 3 and the first light detector 6, and thus it is possible to detect the interference light L1 of the measurement light with a sufficient light amount. As described above, according to the optical module 1A, it is possible to realize high-accuracy spectral analysis with a simple configuration.

In addition, in the optical module 1A, the return light suppressing unit 57 is a part of the second support structure 12 that supports the second mirror 52. Accordingly, it is possible to suppress an increase in the number of parts.

In addition, in the optical module 1A, the filter 54 having a function of allowing the measurement light L0 to be transmitted therethrough and cutting off the laser light L10 is disposed between the light incident unit 4 and the beam splitter unit 3. Accordingly, it is possible to prevent light of sensitivity wavelength component of the second light detector 8 from being incident to the beam splitter unit 3 from the light incident unit 4, and it is possible to acquire a position of the movable mirror 22 in the Z-axis direction with accuracy on the basis of a detection result of the interference light L11 of the laser light. In addition, the filter 54 is disposed in a state of being inclined with respect to an optical axis of the light incident unit 4. Accordingly, it is possible to reflect a part of the interference light L11 of the laser light which is emitted from the beam splitter unit 3 to the light incident unit 4 side to the outside of the interference optical system, and it is possible to prevent a part of the interference light L11 of the laser light from being incident to the beam splitter unit 3 again. As an example, in a case where a Si photodiode is used in the second light detector 8, when the filter 54 is formed of a Si substrate, light of a wavelength of 1000 nm or less is absorbed by the filter 54, but light of a wavelength longer than 1000 nm in light of a sensitivity wavelength component of the Si photodiode is not absorbed. Light of the wavelength longer than 1000 nm is transmitted through the first mirror 51 and is absorbed by the filter 56. In this manner, light of the sensitivity wavelength component of the Si photodiode is removed from light incident from the light incident unit 4 is removed in cooperation of the filter 54 and the filter 56.

In addition, in the optical module 1A, the first light detector 6, the second light detector 8, and the second light source 7 are disposed to be aligned in this order. Accordingly, the first light detector 6 and the second light detector 8 are adjacent to each other, and thus it is possible to realize simplification of a configuration of a circuit substrate for signal input/output with respect to the first light detector 6, the second light detector 8, and the second light source 7.

In addition, in the optical module 1A, the first light detector 6, the second light detector 8, and the second light source 7 are disposed to face the other side in the Z-axis direction on one side of the beam splitter unit 3 in the Z-axis direction. Accordingly, it is possible to realize a reduction in size of the optical module 1A in a direction intersecting the Z-axis direction.

Here, effectiveness of the filter 56 and the return light suppressing unit 57 will be described in more detail. First, in the optical module 1A, when the filter 56 is not disposed between the first mirror 51 and the first light detector 6, a part of the interference light L11 of the laser light may be transmitted through the first mirror 51 and be incident to the first light detector 6. For example, when a part of the interference light L11 of the laser light having a wavelength of 850 nm is incident to the first light detector 6, a foot of a spectrum broadens due to a leakage error. As a result, as illustrated in FIG. 11, a dark level (“dark level before countermeasure” in FIG. 11)” is raised with respect to a spectrum of the measurement light L0. In the optical module 1A, the filter 56 is disposed between the first mirror 51 and the first light detector 6. Accordingly, a part of the interference light L11 of the laser light is prevented from being incident to the first light detector 6, and as illustrated in FIG. 11, the dark level (“dark level after countermeasure” in FIG. 11) is lowered with respect to the spectrum of the measurement light L0. In this manner, in the optical module 1A, the filter 56 having a function of allowing the measurement light L0 to be transmitted therethrough and cutting the laser light L10 is disposed between the first mirror 51 and the first light detector 6, and thus it is possible to reduce noise in a detection result of the interference light L1 of the measurement light. In addition, for example, when the first light source is a halogen lamp or the like, the interference light L1 of the measurement light may be weak light depending on a measurement target. In this case, it is necessary to raise an increase magnification of an output of the first light detector 6. At this time, when a part of the interference light L1 of the laser light for acquiring a position of the movable mirror 22 becomes leaked light, and is detected by the first light detector 6, a noise component caused by the leaked light also increments, and thus it is difficult to detect the interference light L1 of the weak measurement light through a measurement target with accuracy. In the optical module 1A, when a part of the interference light L11 of the laser light becomes leaked light, the leaked light may have a great effect on detection of the interference light L1 of the measurement light, and thus the filter 56 is very important.

In addition, when the return light suppressing unit 57 is not disposed on a side opposite to the second light detector 8 with respect to the second mirror 52, a part of the laser light L reflected by the second mirror 52 may be reflected from a surface 112 a of the light transmitting member 112, a surface of the mirror device 20, or the like, may be incident to the second mirror 52, and may overlap the interference light L1 of the laser light. In this manner, a component other than a component reflected by each of the movable mirror 22 and the fixed mirror 16 is superimposed on the interference light L11 of the laser light, detection accuracy of a position of the movable mirror 22 in the Z-axis direction deteriorates. In the optical module 1A, the return light suppressing unit 57 is disposed on a side opposite to the second light detector 8 with respect to the second mirror 52, and thus a part of the laser light L reflected by the second mirror 52 is not superimposed on the interference light L1 of the laser light. In this manner, in the optical module 1A, the return light suppressing unit 57 having a function of suppressing the incident laser light L10 from becoming return light is disposed on a side opposite to the second light detector 8 with respect to the second mirror 52, and thus it is possible to acquire the position of the movable mirror 22 in the Z-axis direction with accuracy.

Second Embodiment

As illustrated in FIG. 12, an optical module 1B is mainly different from the above-described optical module 1A in a configuration of the second support structure 12 that supports the light incident unit 4, the first light detector 6, the second light source 7, and the second light detector 8. Configurations of the mirror unit 2, the beam splitter unit 3, the support 9, and the first support structure 11 in the optical module 1B are the same as in the above-described optical module 1A.

The second support structure 12 includes a main body portion 140. The main body portion 140 includes a pair of side wall portions 141 and 142, a ceiling wall portion 143, and an extension portion 144. For example, the main body portion 140 is integrally formed of a metal. The main body portion 140 is provided with a plurality of positioning pins 121 a. The main body portion 140 is positioned with respect to the support 9 by inserting the positioning pins 121 a into reference holes 9 b and 9 c formed in the support 9, and in this state, the main body portion 140 is attached to the support 9, for example, by a bolt.

The pair of side wall portions 141 and 142 face each other in the X-axis direction. An opening 141 a is formed in the side wall portion 141 on one side in the X-axis direction. The ceiling wall portion 143 faces the support 9 in the Z-axis direction. An opening 143 a is formed in the ceiling wall portion 143. The extension portion 144 extends from the side wall portion 141 to one side in the X-axis direction. A first through-hole 144 a, a second through-hole 144 b, and a third through-hole 144 c are formed in the extension portion 144. The first through-hole 144 a, the second through-hole 144 b, and the third through-hole 144 c pass through the extension portion 144 along the Z-axis direction. The second through-hole 144 b is formed on one side of the first through-hole 144 a in the X-axis direction. The third through-hole 144 c is formed on one side of the second through-hole 144 b in the X-axis direction.

The light incident unit 4 is disposed in the opening 143 a of the ceiling wall portion 143. The light incident unit 4 includes a holder 41, a collimator lens 42, and a filter (second filter) 43. The holder 41 is provided with an aperture 44. Measurement light L0 incident from the first light source through a measurement target or measurement light L0 that occurs from the measurement target is incident to the aperture 44. The filter 43 is disposed on the light incident unit 4 side with respect to the beam splitter unit 3, and is attached to the holder 41 to close the aperture 44 on a light emission side of the aperture 44. The filter 43 has a function of allowing the measurement light L0 to be transmitted therethrough and cutting off the laser light L10. For example, the filter 43 is formed of silicon in a plate shape. In this embodiment, the filter 43 has a function of allowing the measurement light L0 to be transmitted therethrough and absorbing the laser light L10. In this embodiment, the filter 54 has a function of absorbing the laser light L10 as the function of cutting the laser light L10, but may have a function of reflecting the laser light L10, for example, to the outside of the interference optical system as the function of cutting off the laser light L10. Accordingly, it is possible to prevent light of a sensitivity wavelength component of the second light detector 8 from being incident to the beam splitter unit 3 from the light incident unit 4. The collimator lens 42 is held by the holder 41. The collimator lens 42 collimates the measurement light L0 that is transmitted through the filter 43. The holder 41 is fixed to the ceiling wall portion 143 in the opening 143 a.

The first light detector 6 is disposed in the first through-hole 144 a. The first light detector 6 includes a light detection element 62, a package 64 including a light transmission window 64 a, a holder 61, a condensing lens 63, and a plurality of lead pins 65. The package 64 accommodates the light detection element 62. The light detection element 62 detects the interference light L1 of the measurement light. For example, the light detection element 62 is an InGaAs photodiode. The holder 61 holds the package 64 and the condensing lens 63. The condensing lens 63 condenses the interference light L1 of the measurement light which is incident to the light detection element 62 through the light transmission window 64 a to the light detection element 62. An optical axis of the light detection element 62 and an optical axis of the condensing lens 63 match each other.

The holder 61 is fixed to the extension portion 144 in the first through-hole 144 a. In this manner, the first light detector 6 is disposed on one side of the mirror unit 2 in the X-axis direction to face one side in the Z-axis direction, and is supported by the second support structure 12. The first light detector 6 detects interference light L1 of the measurement light which is emitted from the beam splitter unit 3.

The second light detector 8 is disposed in the second through-hole 144 b. The second light detector 8 includes a light detection element 82, a package 84 including a condensing lens 84 a, and a plurality of lead pins 85. The light detection element 82 detects the interference light L11 of the laser light. For example, the light detection element 82 is a Si photodiode. The condensing lens 84 a condenses the interference light L1 of the laser light which is incident to the light detection element 82 to the light detection element 82. An optical axis of the light detection element 82 and an optical axis of the condensing lens 84 a match each other.

The package 84 is fixed to the extension portion 144 in the second through-hole 144 b. In this manner, the second light detector 8 is disposed on one side of the first light detector 6 in the X-axis direction (on one side of the first optical device in a direction intersecting an optical axis of the first optical device) to face the same side as in the first light detector 6, and is supported by the second support structure 12. The second light detector 8 detects the interference light L11 of the laser light which is emitted from the beam splitter unit 3.

The second light source 7 is disposed in the third through-hole 144 c. The second light source 7 includes a light-emitting element 72, a package 74 including a collimator lens 74 a, and a plurality of lead pins 75. The light-emitting element 72 emits the laser light L10. For example, the light-emitting element 72 is a semiconductor laser such as VCSEL. The collimator lens 74 a collimates the laser light L10 emitted from the light-emitting element 72. An optical axis of the light-emitting element 72 and an optical axis of the collimator lens 74 a match each other.

The package 74 is fixed to the extension portion 144 in the third through-hole 144 c. In this manner, the second light source 7 is disposed on one side of the second light detector 8 in the X-axis direction (on one side of the second optical device in a direction intersecting the optical axis of the first optical device) to face the same side as in the first light detector 6, and is supported by the second support structure 12. The second light source 7 emits the laser light L10 to be incident to the beam splitter unit 3.

As described above, the main body portion 140 of the second support structure 12 (more specifically, the extension portion 144) holds the first light detector 6, the second light detector 8, and the second light source 7 so that the first light detector (first optical device) 6, the second light detector (second optical device) 8, and the second light source (third optical device) 7 face the same side, and are aligned in the order of the first light detector 6, the second light detector 8, and the second light source 7. In this embodiment, the main body portion 140 holds the first light detector 6, the second light detector 8, and the second light source 7 so that the first light detector 6, the second light detector 8, and the second light source 7 face one side in the Z-axis direction on one side of the mirror unit 2 in the X-axis direction. In addition, the main body portion 140 holds the first light detector 6, the second light detector 8, and the second light source 7 so that the first light detector 6, the second light detector 8, and the second light source 7 are aligned in this order from the other side in the X-axis direction (that is, from the mirror unit 2 side).

A first mirror 51, a second mirror 52, and a third mirror 53 are attached to the extension portion 144. The first mirror 51 is attached to the extension portion 144 to be located on one side of the first light detector 6 in the Z-axis direction. The second mirror 52 is attached to the extension portion 144 to be located on one side of the second light detector 8 in the Z-axis direction. The third mirror 53 is attached to the extension portion 144 to be located on one side of the second light source 7 in the Z-axis direction.

The first mirror 51 is a dichroic mirror that has a function of reflecting the measurement light L0 and allowing the laser light L10 to be transmitted therethrough, and is inclined with respect to an optical axis of the first light detector 6. The first mirror 51 is disposed to overlap the beam splitter unit 3 through the opening 141 a of the side wall portion 141 when viewed from the X-axis direction and to overlap the first light detector 6 when viewed from the Z-axis direction. That is, the first mirror 51 is disposed to face the beam splitter unit 3 and the first light detector 6. In this embodiment, an optical surface of the first mirror 51 is a surface that is parallel to the Y-axis direction and has an angle of 45° with respect to the Z-axis direction. The optical axis of the first light detector 6 is parallel to the Z-axis direction.

The second mirror 52 is a mirror (for example, a half mirror) that has a function of reflecting a part of the laser light L10 and allowing the remainder of the laser light L10 to be transmitted therethrough, and is parallel to the first mirror 51. The second mirror 52 is disposed to overlap the first mirror 51 when viewed from the X-axis direction, and to overlap the second light detector 8 when viewed from the Z-axis direction. That is, the second mirror 52 is disposed to face the first mirror 51 and the second light detector 8. In this embodiment, an optical surface of the second mirror 52 is a surface that is parallel to the Y-axis direction and has an angle of 45° with respect to the Z-axis direction.

The third mirror 53 is a mirror (for example, a total reflection mirror) that has a function of reflecting the laser light L10 and is parallel to the second mirror 52. The third mirror 53 is disposed to overlap the second mirror 52 when viewed from the X-axis direction, and to overlap the second light source 7 when viewed from the Z-axis direction. That is, the third mirror 53 is disposed to face the second mirror 52 and the second light source 7. In this embodiment, an optical surface of the third mirror 53 is a surface that is parallel to the Y-axis direction and has an angle of 45° with respect to the Z-axis direction.

A filter 56 is disposed between the first mirror 51 and the first light detector 6. In this embodiment, the filter 56 is held by the holder 61 of the first light detector 6. The filter 56 has a function of allowing the measurement light L0 to be transmitted therethrough and cutting off the laser light L10. For example, the filter 56 is a silicon plate in which an anti-reflection film is formed on a light incident surface. As described above, the filter 56 is a member different from a member in which the first mirror 51 is formed on a surface (surface facing the beam splitter unit 3) on the beam splitter unit 3 side. In this embodiment, the filter 56 has a function of allowing the measurement light L0 to be transmitted therethrough and absorbing the laser light L10. In this embodiment, the filter 56 has the function of absorbing the laser light L10 as the function of cutting off the laser light L10, but may have a function of reflecting the laser light L10, for example, to the outside of the interference optical system as the function of cutting off the laser light L10.

A return light suppressing unit 57 is disposed on a side opposite to the second light detector 8 with respect to the second mirror 52. The return light suppressing unit 57 has a function suppressing incident laser light L10 from becoming return light. In this embodiment, the return light suppressing unit 57 is a part of the second support structure (support) 12 that holds the second mirror 52. More specifically, the return light suppressing unit 57 is a part of the extension portion 144. The return light suppressing unit 57 is constituted by forming a black resist layer on the portion, or by performing a black almite treatment to the portion. In this embodiment, the return light suppressing unit 57 has the function of absorbing the incident laser light L10 as the function of suppressing the incident laser light L10 from becoming return light, but may have a function of reflecting the incident laser light L10, for example, to the outside of the interference optical system as the function of suppressing the incident laser light L10 from becoming return light.

The main body portion 140 of the second support structure 12 is fixed to a wiring substrate 500 by a bolt or the like. The plurality of lead pins 113 of the first support structure 11, the plurality of lead pins 65 of the first light detector 6, the plurality of lead pins 85 of the second light detector 8, and the plurality of lead pins 75 of the second light source 7 are electrically or physically connected to wires of the wiring substrate 500. The wiring substrate 500 is provided with a connector 501 that electrically connects the optical module 1B to an external device.

Here, description will be given of an optical path between the beam splitter unit 3 and the first light detector 6, and the like. Interference light L1 of the measurement light which is emitted from the beam splitter unit 3 along the X-axis direction is reflected by the first mirror 51, and is incident to the first light detector 6 through the filter 56 and is detected by the first light detector 6. On the other hand, the laser light L10 emitted from the second light source 7 is reflected by the third mirror 53, is transmitted through the second mirror 52 and the first mirror 51, and is incident to the beam splitter unit 3 along the X-axis direction. Interference light L11 of the laser light which is emitted from the beam splitter unit 3 along the X-axis direction is transmitted through the first mirror 51, is reflected by the second mirror 52, and is incident to the second light detector 8 and is detected by the second light detector 8. On the other hand, a part of the laser light L10 reflected by the second mirror 52 is suppressed from becoming return light due to the return light suppressing unit 57.

In the optical module 1B, a length of the optical path between the beam splitter unit 3 and the first light detector 6 is shorter than a length of an optical path between the beam splitter unit 3 and the second light detector 8, and is shorter than a length of an optical path between the beam splitter unit 3 and the second light source 7. The lengths of the optical paths represent physical distances along the optical paths.

Specifically, a distance from an intersection between an optical path and the first mirror surface 31 of the beam splitter unit 3 to a light incident surface of the first light detector 6 is shorter than a distance from an intersection between an optical path and the first mirror surface 31 of the beam splitter unit 3 to a light incident surface of the second light detector 8, and is shorter than a distance from an intersection between an optical path and the first mirror surface 31 of the beam splitter unit 3 to a light emission surface of the second light source 7.

A distance from an intersection between an optical path and the first mirror surface 31 of the beam splitter unit 3 to a light incident surface of the condensing lens 63 of the first light detector 6 is shorter than a distance from an intersection between an optical path and the first mirror surface 31 of the beam splitter unit 3 to a light incident surface of the condensing lens 84 a of the second light detector 8, and is shorter than a distance from an intersection between an optical path and the first mirror surface 31 of the beam splitter unit 3 to a light emission surface of the collimator lens 74 a of the second light source 7. A distance from the optical surface 33 a of the beam splitter unit 3 to the light incident surface of the first light detector 6 is shorter than a distance from the optical surface 33 a of the beam splitter unit 3 to the light incident surface of the second light detector 8, and is shorter than a distance from the optical surface 33 a of the beam splitter unit 3 to the light emission surface of the second light source 7. A distance from the optical surface 33 a of the beam splitter unit 3 to the light incident surface of the condensing lens 63 of the first light detector 6 is shorter than a distance from optical surface 33 a of the beam splitter unit 3 to the light incident surface of the condensing lens 84 a of the second light detector 8, and is shorter than a distance from the optical surface 33 a of the beam splitter unit 3 to the light emission surface of the collimator lens 74 a of the second light source 7.

According to the optical module 1B configured as described above, it is possible to realize high-accuracy spectral analysis with a simple configuration as in the above-described optical module 1B.

In addition, in the optical module 1B, the first light detector 6, the second light detector 8, and the second light source 7 are disposed to one side in the Z-axis direction on one side of the mirror unit 2 in the X-axis direction. Accordingly, it is possible to realize a reduction in size of the optical module 1B in the Z-axis direction.

Third Embodiment

As illustrated in FIG. 13, an optical module 1C includes a first light source 5 that emits the measurement light L0. The first light source 5 includes a light-emitting element 5 a, and a collimator lens 5 c. For example, the light-emitting element 5 a is a heat type light source such as a filament. The collimator lens 5 c collimates the measurement light L0.

The holding unit 130 holds the first light source 5, the second light source 7, and the second light detector 8 so that the first light source (first optical device) 5, the second light source (second optical device) 7, and the second light detector (third optical device) 8 are face the other side (that is, the beam splitter unit 3 side) in the Z-axis direction on one side of the beam splitter unit 3 in the Z-axis direction, and are aligned in the order of the first light source 5, the second light source 7, and the second light detector 8 from the one side in the X-axis direction.

A holding unit 130 holds a first mirror 51, a second mirror 52, and a third mirror 53 in addition to the first light source 5, the second light source 7, and the second light detector 8. The first mirror 51, the second mirror 52, and the third mirror 53 are constituted by a plurality of optical plates which are separated from each other.

The first mirror 51 is a dichroic mirror that has a function of allowing the measurement light L0 to be transmitted therethrough and reflecting the laser light L10, and is inclined with respect to an optical axis of the first light source 5. The first mirror 51 is disposed between the beam splitter unit 3 and the first light source 5. That is, the first mirror 51 is disposed to face the beam splitter unit 3 and the first light source 5. An aperture 55 that is held by the holding unit 130 is disposed between the first mirror 51 and the first light source 5. In this embodiment, an optical surface of the first mirror 51 is a surface that is parallel to the Y-axis direction and has an angle of 45° with respect to the Z-axis direction. The optical axis of the first light source 5 is parallel to the Z-axis direction.

The second mirror 52 is a mirror that has a function of reflecting a part of the laser light L10 and allowing the remainder of the laser light L10 to be transmitted therethrough and is parallel to the first mirror 51. The second mirror 52 is disposed to overlap the first mirror 51 when viewed from the X-axis direction and to overlap the second light source 7 when viewed from the Z-axis direction. That is, the second mirror 52 is disposed to face the first mirror 51 and the second light source 7. In this embodiment, an optical surface of the second mirror 52 is a surface that is parallel to the Y-axis direction and has an angle of 45° with respect to the Z-axis direction.

The third mirror 53 is a mirror that has a function of reflecting the laser light L10 and is parallel to the second mirror 52. The third mirror 53 is disposed to overlap the second mirror 52 when viewed from the X-axis direction and to overlap the second light detector 8 when viewed from the Z-axis direction. That is, the third mirror 53 is disposed to face the second mirror 52 and the second light detector 8. In this embodiment, an optical surface of the third mirror 53 is a surface that is parallel to the Y-axis direction and has an angle of 45° with respect to the Z-axis direction.

In the optical module 1C, the measurement light L0 that is emitted from the first light source 5 along the Z-axis direction is incident to the first mirror 51 through the aperture 55, is transmitted through the first mirror 51, and is incident to the optical surface 33 a of the beam splitter unit 3 along the Z-axis direction. Interference light L1 of the measurement light which is emitted from the optical surface 33 d of the beam splitter unit 3 along the X-axis direction is emitted to the outside of a housing 10 through a window 10 a provided in the housing 10 while being condensed by a condensing lens 58 a, and is emitted to a measurement target (not illustrated). The interference light L1 of the measurement light which is reflected from the measurement target is incident into the housing 10 through the window 10 a and is condensed by a condensing lens 58 b. The condensed interference light L1 of the measurement light is incident to the first light detector 6 along the Z-axis direction, and is detected by the first light detector 6.

On the other hand, the laser light L10 that is emitted from the second light source 7 is reflected by the second mirror 52 and the first mirror 51, and is incident to an optical surface 33 a of the beam splitter unit 3 along the Z-axis direction. Interference light L11 of the laser light which is emitted from the optical surface 33 a of the beam splitter unit 3 along the Z-axis direction is reflected by the first mirror 51, is transmitted through the second mirror 52, is reflected by the third mirror 53, and is incident to the second light detector 8 and is detected by the second light detector 8.

In the optical module 1C, a filter 56 having a function of allowing the measurement light L0 to be transmitted therethrough and cutting off the laser light L10 is disposed on an optical path between the beam splitter unit 3 and the first light detector 6. In addition, a filter 54 having a function of allowing the measurement light L0 to be transmitted therethrough and cutting off the laser light L10 is provided on an optical path between the first light source 5 and the first mirror 51. In addition, a return light suppressing unit 57 having a function of suppressing incident laser light L10 from becoming return light is provided on a side opposite to the second light source 7 with respect to the second mirror 52.

In the optical module 1C, a length of an optical path between the beam splitter unit 3 and the first light source 5 is shorter than a length of an optical path between the beam splitter unit 3 and the second light source 7, and is shorter than a length of an optical path between the beam splitter unit 3 and the second light detector 8. The lengths of the optical paths represent physical distances along the optical paths.

Specifically, a distance from an intersection between an optical path and the first mirror surface 31 of the beam splitter unit 3 to a light emission surface of the first light source 5 is shorter than a distance from an intersection between an optical path and the first mirror surface 31 of the beam splitter unit 3 to a light emission surface of the second light source 7, and is shorter than a distance from an intersection between an optical path and the first mirror surface 31 of the beam splitter unit 3 to a light incident surface of the second light detector 8. A distance from an intersection between the optical path and the first mirror surface 31 of the beam splitter unit 3 to a light emission surface of the collimator lens 5 c of the first light source 5 is shorter than a distance from an intersection between an optical path and the first mirror surface 31 of the beam splitter unit 3 to a light emission surface of the collimator lens 74 a of the second light source 7, and is shorter than a distance from an intersection between an optical path and the first mirror surface 31 of the beam splitter unit 3 to an optical surface 33 a of the condensing lens 84 a of the second light detector 8. A distance from the optical surface 33 a of the beam splitter unit 3 to the light emission surface of the first light source 5 is shorter than a distance from the optical surface 33 a of the beam splitter unit 3 to the light emission surface of the second light source 7, and is shorter than a distance from the optical surface 33 a of the beam splitter unit 3 to the light incident surface of the second light detector 8. A distance from the optical surface 33 a of the beam splitter unit 3 to the light emission surface of the collimator lens 5 c of the first light source 5 is shorter than a distance from the optical surface of the beam splitter unit 3 to the light emission surface of the collimator lens 74 a of the second light source 7 and is shorter than a distance from the optical surface 33 a of the beam splitter unit 3 to the light incident surface of the condensing lens 84 a of the second light detector 8.

In the optical module 1C configured as described above, the first light source 5, the second light source 7, and the second light detector 8 are disposed to face the same side. Accordingly, it is possible to constitute the interference optical system relating to the measurement light L0 and the interference optical system relating to the laser light L10 with a simple layout, and it is possible to carry out spectral analysis on the basis of a detection result of the interference light L1 of the measurement light while acquiring a position of the movable mirror 22 in the Z-axis direction on the basis of a detection result of the interference light L11 of the laser light. In addition, the return light suppressing unit 57 having a function of suppressing incident laser light L10 from becoming return light is disposed on a side opposite to the second light source 7 with respect to the second mirror 52. Accordingly, it is possible to prevent a component other than a component reflected by each of the movable mirror 22 and the fixed mirror 16 from being superimposed on the interference light L11 of the laser light, and thus it is possible to acquire a position of the movable mirror 22 in the Z-axis direction with accuracy. In addition, the first light source 5, the second light source 7, and the second light detector 8 are disposed to be aligned in this order. Accordingly, it is possible to shorten a length of an optical path between the first light source 5 and the beam splitter unit 3, and thus it is possible to detect the interference light L1 of the measurement light with a sufficient light amount. As described above, according to the optical module 1C, it is possible to realize high-accuracy spectral analysis with a simple configuration.

In addition, in the optical module 1C, the first light source 5, the second light source 7, and the second light detector 8 are disposed to be aligned in this order. Accordingly, the first light source 5 and the second light source 7 are adjacent to each other, and thus it is possible to realize simplification of a configuration of a circuit substrate for signal input/output with respect to the first light source 5, the second light source 7, and the second light detector 8.

In addition, in the optical module 1C, on one side of the beam splitter unit 3 in the Z-axis direction, the first light source 5, the second light source 7, and the second light detector 8 are disposed to face the other side in the Z-axis direction. Accordingly, it is possible to realize a reduction in size of the optical module 1C in a direction intersecting the Z-axis direction.

Fourth Embodiment

As illustrated in FIG. 14, in an optical module 1D, a holding unit 130 holds a first light source 5, a second light source 7, and a second light detector 8 so that the first light source (first optical device) 5, the second light source (second optical device) 7, and the second light detector (third optical device) 8 face one side in the Z-axis direction on one side of a mirror unit 2 in the X-axis direction, and are aligned in the order of the first light source 5, the second light source 7, and the second light detector 8 from the other side (that is, the mirror unit 2 side) in the X-axis direction.

The holding unit 130 holds a first mirror 51, a second mirror 52, and a third mirror 53 in addition to the first light source 5, the second light source 7, and the second light detector 8. The first mirror 51, the second mirror 52, and the third mirror 53 are constituted by a plurality of optical blocks which are joined to each other.

The first mirror 51 is a dichroic mirror that has a function of reflecting the measurement light L0 and allowing the laser light L10 to be transmitted therethrough and is inclined with respect to an optical axis of the first light source 5. The first mirror 51 is disposed to overlap a beam splitter unit 3 when viewed from the X-axis direction, and to overlap the first light source 5 when viewed from the Z-axis direction. That is, the first mirror 51 is disposed to face the beam splitter unit 3 and the first light source 5. In this embodiment, an optical surface of the first mirror 51 is a surface that is parallel to the Y-axis direction and has an angle of 45° with respect to the Z-axis direction. The optical axis of the first light source 5 is parallel to the Z-axis direction.

The second mirror 52 is a mirror that has a function of reflecting a part of the laser light L10 and allowing the remainder of the laser light L10 to be transmitted therethrough and is parallel to the first mirror 51. The second mirror 52 is disposed to overlap the first mirror 51 when viewed from the X-axis direction and to overlap the second light source 7 when viewed from the Z-axis direction. That is, the second mirror 52 is disposed to face the first mirror 51 and the second light source 7. In this embodiment, an optical surface of the second mirror 52 is a surface that is parallel to the Y-axis direction and has an angle of 45° with respect to the Z-axis direction.

The third mirror 53 is a mirror that has a function of reflecting the laser light L10 and is parallel to the second mirror 52. That is, third mirror 53 is disposed to overlap the second mirror 52 when viewed from the X-axis direction and to overlap the second light detector 8 when viewed from the Z-axis direction. That is, the third mirror 53 is disposed to face the second mirror 52 and the second light detector 8. In this embodiment, an optical surface of the third mirror 53 is a surface that is parallel to the Y-axis direction and has an angle of 45° with respect to the Z-axis direction.

In the optical module 1D, the measurement light L0 that is emitted from the first light source 5 along the Z-axis direction is reflected by the first mirror 51, and is incident to an optical surface 33 d of the beam splitter unit 3 along the X-axis direction. Interference light L1 of the measurement light which is emitted from an optical surface 33 a of the beam splitter unit 3 along the Z-axis direction is emitted to the outside of a housing 10 through a window 10 a provided in the housing 10 while being condensed by a condensing lens 58 a, and is emitted to a measurement target (not illustrated). The interference light L1 of the measurement light which is reflected from the measurement target is incident into the housing 10 through the window 10 a and is condensed by a condensing lens 58 b. The condensed interference light L1 of the measurement light is incident to the first light detector 6 along the X-axis direction, and is detected by the first light detector 6.

On the other hand, the laser light L10 emitted from the second light source 7 is reflected by the second mirror 52, is transmitted through the first mirror 51, and is incident to the optical surface 33 d of the beam splitter unit 3 along the X-axis direction. Interference light L11 of the laser light which is emitted from the optical surface 33 d of the beam splitter unit 3 along the X-axis direction is transmitted through the first mirror 51 and the second mirror 52, is reflected by the third mirror 53, and is incident to the second light detector 8 and is detected by the second light detector 8.

In the optical module 1D, a filter 56 having a function of allowing the measurement light L0 to be transmitted therethrough and cutting off the laser light L10 is disposed on an optical path between the beam splitter unit 3 and the first light detector 6. In addition, a filter 54 having a function of allowing the measurement light L0 to be transmitted therethrough and cutting off the laser light L10 is disposed on an optical path between the first light source 5 and the first mirror 51. In addition, a return light suppressing unit 57 having a function of suppressing incident laser light L10 from becoming return light is disposed on a side opposite to the second light source 7 with respect to the second mirror 52.

In the optical module 1D, a length of an optical path between the beam splitter unit 3 and the first light source 5 is shorter than a length of an optical path between the beam splitter unit 3 and the second light source 7, and is shorter than a length of an optical path between the beam splitter unit 3 and the second light detector 8. The lengths of the optical paths represent physical distances along the optical paths.

Specifically, a distance from an intersection between an optical path and the first mirror surface 31 of the beam splitter unit 3 to a light emission surface of the first light source 5 is shorter than a distance from an intersection between an optical path and the first mirror surface 31 of the beam splitter unit 3 to a light emission surface of the second light source 7, and is shorter than a distance from an intersection between an optical path and the first mirror surface 31 of the beam splitter unit 3 to a light incident surface of the second light detector 8. A distance from an intersection between an optical path and the first mirror surface 31 of the beam splitter unit 3 to a light emission surface of a condensing lens 5 b of the first light source 5 is shorter than a distance from an intersection between an optical path and the first mirror surface 31 of the beam splitter unit 3 to a light emission surface of a collimator lens 74 a of the second light source 7, and is shorter than a distance from an intersection between an optical path and the first mirror surface 31 of the beam splitter unit 3 to a light incident surface of a condensing lens 84 a of the second light detector 8. A distance from the optical surface 33 d of the beam splitter unit 3 to the light emission surface of the first light source 5 is shorter than a distance from the optical surface 33 d of the beam splitter unit 3 to the light emission surface of the second light source 7, and is shorter than a distance from the optical surface 33 d of the beam splitter unit 3 to the light incident surface of the second light detector 8. A distance from the optical surface 33 d of the beam splitter unit 3 to the light emission surface of the condensing lens 5 b of the first light source 5 is shorter than a distance from the optical surface 33 d of the beam splitter unit 3 to the light emission surface of the collimator lens 74 a of the second light source 7, and is shorter than a distance from the optical surface 33 d of the beam splitter unit 3 to the light incident surface of the condensing lens 84 a of the second light detector 8.

According to the optical module 1D configured as described above, as in the above-described optical module 1C, it is possible to realize high-accuracy spectral analysis with a simple configuration.

In addition, in the optical module 1D, the first light source 5, the second light source 7, and the second light detector 8 are disposed to face one side in the Z-axis direction on one side of the mirror unit 2 in the X-axis direction. Accordingly, it is possible to realize a reduction in size of the optical module 1B in the Z-axis direction.

Modification Example

The present disclosure is not limited to the above-described embodiments. For example, the optical module 1A of the first embodiment and the optical module 1B of the second embodiment may include the first light source 5 that emits the measurement light L0. In addition, in the optical module 1A of the first embodiment and the optical module 1B of the second embodiment, the second light source 7 may be disposed on one side of the first light detector 6 in a direction interesting the optical axis of the first light detector 6, and the second light detector 8 may be disposed on one side of the second light source 7 in the direction. In addition, in the optical module 1C of the third embodiment and the optical module 1D of the fourth embodiment, the second light detector 8 may be disposed on one side of the first light source 5 in a direction intersecting the optical axis of the first light source, and the second light source 7 may be disposed on one side of the second light detector 8 in the direction.

In addition, in the optical module 1A of the first embodiment and the optical module 1B of the second embodiment, the same side which the first light detector 6, the second light source 7, and the second light detector 8 face is not limited to one side in the Z-axis direction and the other side in the Z-axis direction, and the same side may be, for example, the beam splitter unit 3 side in the X-axis direction. In addition, in the optical module 1C of the third embodiment and the optical module 1D of the fourth embodiment, the same side which the first light source 5, the second light source 7, and the second light detector 8 face is not limited to one side in the Z-axis direction and the other side in the Z-axis direction, and may be, for example, the beam splitter unit 3 side in the X-axis direction.

In addition, there is no limitation to the above-described aspects as long as the mirror unit 2, the base 21, the movable mirror 22, and the fixed mirror 16 are included. For example, the fixed mirror 16 may be provided in the mirror device 20. In addition, the mirror surface 16 a of the fixed mirror 16 may not face the same side as in the mirror surface 22 a of the movable mirror 22. In addition, the mirror unit 2 may include a plurality of the fixed mirrors 16. In this case, the interference optical system relating to the measurement light L0 and the interference optical system relating to the laser light L10 may be constituted by separate fixed mirrors 16.

In addition, in the mirror device 20, the light passage portion 24 may be a notch that is formed in the base 21. Similarly, in the mirror device 20, the light passage portion 25 may be a notch that is formed in the base 21. In addition, in the mirror device 20, the light passage portion 24 may not be provided. In this case, in a portion that does not overlap the mirror device 20 in the optical function member 13, the light transmitting portion 14 may be provided.

In addition, the optical function member 13 may be provided with a light passage portion such as a hole or a notch instead of the light transmitting portion 14. Similarly, the optical function member 13 may be provided with a light passage portion such as a hole and a notch instead of the light transmitting portion 15.

In addition, in the mirror device 20, the drive unit 23 may include a three or greater elastic support units which elastically support the movable mirror 22. In addition, in the mirror device 20, the drive unit 23 is not limited to a configuration in which the drive unit 23 is constituted by the electrostatic actuator, and may be constituted, for example, by a piezoelectric type actuator, an electromagnetic type actuator, or the like. In addition, the mirror device 20 may be configured in such a manner that the device layer 102 is disposed on the first surface 21 a side, and the support layer 101 is disposed on the second surface 21 b side.

In addition, the second surface 21 b of the base 21 and the third surface 13 a of the optical function member 13 may be joined to each other by means (for example, an adhesive such as an UV-curable resin, glass frit, a solder material, or the like) other than direct bonding. In addition, the fixed mirror 16 may be separated from the fourth surface 13 b of the optical function member 13 as long as the fixed mirror 16 is disposed on a side opposite to the mirror device 20 with respect to the optical function member 13.

In addition, the beam splitter unit 3 may be constituted by one optical block including the first mirror surface 31 and the second mirror surface 32. In addition, the beam splitter unit 3 may be constituted by an optical plate including the first mirror surface 31 and a member including the second mirror surface 32. In this case, a region between the first mirror surface 31 and the second mirror surface 32 may be a space.

In addition, in the optical module 1A of the first embodiment, the optical module 1B of the second embodiment, and the optical module 1C of the third embodiment, the first mirror 51, the second mirror 52, and the third mirror 53 may be constituted by a plurality of optical blocks which are joined to each other as in the optical module 1D of the fourth embodiment. In addition, in the optical module 1D of the fourth embodiment, the first mirror 51, the second mirror 52, and the third mirror 53 may be constituted by a plurality of optical plates which are separated from each other as in the optical module LA of the first embodiment.

In addition, for example, the aperture 55 and the filter 56 may be supported by the second support structure 12 without limitation to a configuration in which the aperture 55 and the filter 56 are held by the holder 61 of the first light detector 6. However, the aperture 55 may not be provided. In addition, the member which is different from the filter 56 and in which the first mirror 51 is formed is not limited to the member in which the first mirror 51 is formed on a surface on the beam splitter unit 3 side, and may be a member in which the first mirror 51 is formed on a surface opposite to the beam splitter unit 3, a member in which the first mirror 51 is formed on an inner side, or the like. That is, in this case, the filter 56 may be a member that is different from the member in which the first mirror 51 is formed. In addition, the filter 56 may be a member (a base material of the first mirror 51) in which the first mirror 51 is formed on a surface on the beam splitter unit 3 side, a member in which the first mirror 51 is formed on a surface on a side opposite to the beam splitter unit 3, a member in which the first mirror 51 is formed on an inner side, or the like. That is, in this case, the filter 56 may be the member in which the first mirror 51 is formed. As a specific example, the first mirror 51 may be formed on a surface of a substrate formed of silicon, and the substrate may function as the filter 56. In the cases, it is possible to suppress an increase in the number of parts. In addition, the return light suppressing unit 57 may be a member different from the second support structure (support) 12 that supports the second mirror 52. Examples of the return light suppressing unit 57 includes a silicon plate that is subjected to anti-reflection (AR) coating is performed, a plate on which a black resist layer is formed, a plate that is subjected to a black almite treatment, and the like, and the return light suppressing unit 57 may be disposed on the light transmitting member 112 of the first support structure 11. In this case, it is possible to improve the degree of freedom of design of the second support structure 12 and the return light suppressing unit 57.

In addition, in the configurations of the optical modules 1A, 1B, 1C, and 1D, there is no limitation to the above-described materials and shapes, and various materials and shapes are applicable to the configurations. In addition, the configurations of the first embodiment and the modification example are applicable to the configurations in another embodiment and the modification example in an arbitrary manner.

According to the present disclosure, it is possible to provide an optical module capable of realizing high-accuracy spectral analysis with a simple configuration. 

What is claimed is:
 1. An optical module comprising: a mirror unit that includes a base that has a first surface, a movable mirror that is supported in the base to be movable along a first direction intersecting the first surface, and a fixed mirror of which a position with respect to the base is fixed; a beam splitter unit that is disposed on one side of the mirror unit in the first direction, and constitutes an interference optical system in combination with the movable mirror and the fixed mirror; a light incident unit that causes measurement light that is incident from a first light source through a measurement target or measurement light from a measurement target to be incident to the beam splitter unit; a first optical device that is a first light detector that detects interference light of the measurement light which is emitted from the beam splitter unit; a second optical device that is one of a second light source that emits laser light to be incident to the beam splitter unit or a second light detector that detects interference light of the laser light which is emitted from the beam splitter unit, and is disposed on one side of the first optical device in a direction intersecting an optical axis of the first optical device to face the same side as in the first optical device; a third optical device that is the other of the second light source or the second light detector, and is disposed on the one side of the second optical device in the direction intersecting the optical axis of the first optical device to face the same side as in the first optical device; a first mirror that is disposed to face the beam splitter unit and the first optical device as a dichroic mirror that i) a) allows the measurement light to be transmitted therethrough and b) reflects the laser light or ii) a) reflects the measurement light and b) allows the laser light to be transmitted therethrough, and is inclined with respect to the optical axis of the first optical device; a second mirror that is disposed to face the first mirror and the second optical device as a mirror that i) reflects a part of the laser light, and ii) allows the remainder of the laser light to be transmitted therethrough, and is parallel to the first mirror; a third mirror that is disposed to face the second mirror and the third optical device as a mirror that reflects the laser light, and is parallel to the second mirror; and a return light suppressing unit that suppresses the incident laser light from becoming return light, and is disposed on a side opposite to the second optical device.
 2. The optical module according to claim 1, wherein the return light suppressing unit is a part of a support that supports the second mirror.
 3. The optical module according to claim 1, wherein the return light suppressing unit is a member different from a support that supports the second mirror.
 4. The optical module according to claim 1, further comprising: a filter that allows the measurement light to be transmitted therethrough and cuts off the laser light, and is disposed on the light incident unit side with respect to the beam splitter unit.
 5. The optical module according to claim 1, wherein the second optical device is the second light detector, and the third optical device is the second light source.
 6. The optical module according to claim 1, wherein on the one side of the beam splitter unit in the first direction, the first optical device, the second optical device, and the third optical device are disposed to face the other side in the first direction.
 7. The optical module according to claim 1, wherein on one side of the mirror unit in a second direction intersecting the first direction, the first optical device, the second optical device, and the third optical device are disposed to face the one side in the first direction.
 8. An optical module comprising: a mirror unit that includes a base that has a first surface, a movable mirror that is supported in the base to be movable along a first direction intersecting the first surface, and a fixed mirror of which a position with respect to the base is fixed; a beam splitter unit that is disposed on one side of the mirror unit in the first direction, and constitutes an interference optical system in combination with the movable mirror and the fixed mirror; a first optical device that is a first light source that emits measurement light to be incident to the beam splitter unit; a first light detector that detects interference light of the measurement light which is emitted from the beam splitter unit and is incident through a measurement target; a second optical device that is one of a second light source that emits laser light to be incident to the beam splitter unit r a second light detector that detects interference light of the laser light which is emitted from the beam splitter unit, and is disposed on one side of the first optical device in a direction intersecting an optical axis of the first optical device to face the same side as in the first optical device; a third optical device that is the other of the second light source or the second light detector, and is disposed on the one side of the second optical device in the direction intersecting the optical axis of the first optical device to face the same side as in the first optical device; a first mirror that is disposed to face the beam splitter unit and the first optical device as a dichroic mirror that i) a) allows the measurement light to be transmitted therethrough and b) reflects the laser light or ii) a) reflects the measurement light and b) allows the laser light to be transmitted therethrough, and is inclined with respect to the optical axis of the first optical device; a second mirror that is disposed to face the first mirror and the second optical device as a mirror that i) reflects a part of the laser light, and ii) allows the remainder of the laser light to be transmitted therethrough, and is parallel to the first mirror; a third mirror that is disposed to face the second mirror and the third optical device as a mirror that reflects the laser light, and is parallel to the second mirror; and a return light suppressing unit that suppresses the incident laser light from becoming return light, and is disposed on a side opposite to the second optical device with respect to the second mirror.
 9. The optical module according to claim 8, wherein the second optical device is the second light source, and the third optical device is the second light detector. 